How do I ignore my mother's negativity?

'How can I be a better daughter?' you ask. You already are a good enough daughter I imagine. Change your narrative. Put yourself first and do what you can first and foremost not what you think you 'should' or 'have to' to. This should/have to narrative in my opinion, leads to resentment. This resentment then manifests in unpleasant behaviour. The consequences are when we are not doing the best for ourselves, we don't give of our best to the people around us. I have learnt this now. My mum, older that yours now, can say mean critical things etc. Well she always resorts to such words after I , my sisters too, spend time with her. It can sometimes be after 2 mins. She can't /won't/ doesn't know how to help change this behaviour. She constantly hurts the ppl around her. I have decided to take back my power and not give it away anymore. It works a treat! I still see/do things for her but I follow my internal guide. My visits are limited now and not so often. NO is a word I use now, not completely comfortably, but the more I use it with her the easier it is getting to say it. I don't justify/explain my no. I say it politely, calmly and with love. She is starting to accept it. What she says behind my back is of no interest to me anymore. When I cared what she may/most prob said behind my back, I couldn't confidently say no. I have decided what I can/will do for her. I know what my limits are and I'm not ashamed to put myself first now. It's called self love in my book. My mum may/prob call it selfish. And that's ok with me.

"She has always been this way" says it all.
You can't change anyone, and especially you can't change an elder who's "always been this way".
You are moving her closer to you. You will now need to set in place boundaries. If you need to seek out a counselor to do that, do so. And never move her in with you no matter what.
I am dreadfully sorry about your Sister's suicide. This life is just too tough for some. I think you know that suicide is not so much caused by others, as by our reactions to other, and by our being unable to know how to protect ourselves from others.
You ask us how to be a better daughter? A good daughter understands that they are born to a human being who is flawed in one way or another. A good daughter knows that there is little to be done for a negative or narcissist personality but to protect ones self and ones own family from that person and their negativity. If you don't fully understand that do seek help for yourself. This isn't about "being a good daughter". That is something your Mom will likely never see you as, never tell you, as she is quite wrapped up in herself. This is about taking care of your SELF. That is your prime imperative.
I wish you the best. You have a lot on your plate and a lot of family history. I really encourage you to seek help.

I'm sorry your sister felt the need to commit suicide.

Mom needs something else to occupy her time.

Look up the "grey rock" method and see if you can use it. Can someone take Mom out for the day? Nice lunch and maybe a little shopping, sitting in a park? While she is gone, finish that packing.

If you are moving Mom nearer you, you will need to have boundries. You need to find what resources there are in your area Mom can take advantage of by calling Office of Aging. Senior bus she can use for appts and shopping for one. Set up a day for shopping and running errands. Unless she has major health problems she needs to do for herself. Do not disabled her.

Boundries by Townsend and Cloud is a good book and Christain based. When her complaining gets too much, tell her you just can't listed to it anymore. This is her life, how it goes is all up to her. You can't do everything for her, she has to do it herself. You don't have to stay when she starts and you don't have to pick up the phone when she calls.

Kelly,

I totally understand where you're coming from with your mother. My mother is exactly like this. I am in a place now where if I wasn't leaving soon, I would very likely be driven to an act of desperation.
I've reunited with my ex-husband and am moving with him sans my mother. She's on her own. I have a sibling and she can take over now. I made the good and happy life she's enjoyed with her husband for many years possible. She never took on any of the caregiving responsibility. She's going to find herself in caregiver bootcamp soon enough.
It's kind of you to move her closer. DO NOT for any reason allow her to move in with you! Not even temporarily. When her senior apartment is set up, put her there and let that be the end of it. What will then happen is that because she's closer to you she will become more demanding of your time and more abusive. Now is the time for you and your family to set very strong boundaries and do not let them be breached. If she talks crap about your daughter and SIL but is nice as pie to their faces, call her out on it in front of them. Put her on the spot and force her to explain to these two people what her problem is with them. Do not keep her secrets. Very likely she talks about you to your daughter too. Call her out on it.
Believe me a little embarrassment is exactly what a senior brat like your mother needs. Call her out on her BS and make her explain herself. This is what I do and it works.
My mother pulls this crap all the time and gets called out on it too. She has even taken to calling my son to whisper-complain and talk about me because she thinks I can't hear. When she starts, he hangs up on her. Then she gets called out on it by me and I tell to stop lying about me to my son. You have to call people like our mothers out. If dementia is the reason for their behavior, they belong in a facility or with home caregivers. Their family should limit their exposure to them.
There is nothing you can do to be a better daughter. I am sure that like me you are doing more for your mother than she actually deserves. That's good enough.
You cannot let her hijack your life. She will try to because misery loves company. Keep in mind that her constant negativity, misery, and manipulation helped drive your sister of blessed memory to her grave (may she rest in peace). There's a reason why nearly 50% of caregivers die before the people they are caregivers to. Suicide is the cause of many of those deaths. I've been there. I'm more fortunate than your sister of blessed memory because my ex-husband is a mensch and the best man God ever made.
Please, for your sake and your family's put up those boundaries with your mother. DO NOT let her hijack your life. Tell her exactly what I told mine. Either she cleans up her act and stops with the complaining and senior brat behavior, or the day I move will be the last time she sees or speaks to me. Screen your calls. You don't have to answer all of them. Schedule visiting hours with her during the week and no more. If complaining or negativity start you end a phone call or a visit immediately. Your mother sounds like she complains for entertainment. Many old people do, my mom included. She can find a senior complain group where she will be living. Don't you become her complain group. Good luck.

You have been through a lot. So has your mom.
While it is great that you want to have her move closer so you do not have to travel so far if something happens PLEASE do not move her into your house even on a "temporary" basis until you can find "a place she will like better". Because it won't be temporary because she won't find a place she will like better. There will always be something wrong.
Stop trying to make her life easier, it is just making yours more difficult.
If mom is negative, has pushed all her friends away with the negativity she is going to have to accept that it is on her to change.
I think you have asked the wrong question for the last one.
"How can I be a better daughter?"
Please change this to
"How can she be a better mother?"
Most likely she can't. This is how she is and unless SHE changes this is how it will be.
You change your reaction to what she does.
If the negativity gets to be more than you can handle you step back. Hang up the phone, walk out of the room whatever you need to do to distance yourself.

I know you have said she has always been like this but the past few years even worse. From what you have written she lost a grandson, lost a daughter, lost her husband. has she talked to anyone? Is there a possibility that she might be depressed and would do better with medication and therapy?

Kelly, I am so sorry for your losses!

I understand your impulse to move mom closer, so that you don't have to travel so far to help her. But please don't move her into your home.

Some folks LOVE to complain, but never to the people they have issues with. If mom complains about something that is not within your locus of control, tell her "you'll have to speak to THEM about that, mom."

When it comes to getting help, some folks rely on F.O.G. Fear, Obligation and Guilt. It sounds like what your mom is doing.

Folks like this often play their children and grandchildren off against each other, I guess as a means of ensuring that there will never be agreement or collusion among family members about how much to help, and how. Keep everyone feeling guilty and tense. No boundaries, no ability to say "no, I can't possibly do that."