Any advice for when SIL calls to tell me what to do?

That's a lot of nerve in your SIL! She has no right to demand her mother's jewelry when her brother (your husband) should have right to half (assuming no other siblings). And to demand your husband's jewelry! Oh, my.

I admit I don't understand the "she signed off on inheritance when she asked an attorney to become Guardian..." 

Anyway, tell her she's premature in demanding jewelry, and go find some roadkill instead...

I think she may have dementia. Smile and nod.

I have a feeling there's a long history between you two. She sounds like a pill of a person. What's her history? Has she ever been involved with her mom or her brother? Is this usual for her? If it is, I'd just shut her out.

Is the jewelry worth a lot of money? I might send her one piece from her mom and your husband if you feel like being generous. I'd just let her instructions for care go in one ear and out the other. If you feel like talking to her at all. She may have some dementia as well if it runs in the family. I'd certainly minimize contact with her. Tell us more of the story to help us give better suggestions.

The jewelry, and anything else of value if there is anything left when her mother and brother die, will be distributed as their wills specify. It is likely, though, that their care will require all of their resources. Few people with dementia or other expensive chronic conditions who are not immensely wealthy when they start out have much to leave to heirs when the time comes. Many are lucky if they can pay their own way without taxpayer help. Speaking of which, giving anything of value away before they die would complicate applying for Medicaid if that should ever be necessary.

Unless it is already too late to maintain some peace in the family, I think I'd keep contact with SIL brief, without being rude. "Oh. Someone is at the door and I'm expecting a delivery. We'll talk again soon. Bye."

Response to her advice about her Mother's care, "I'll keep that in mind."

As for what she wants when they die, "I have no control over that, but I'll keep your request in mind. You may want to talk to your mother's guardian regarding requests about her things."

She doesn't sound like someone who can be reasoned with, so I just wouldn't engage on those subjects.

Where is MIL now? Will that change when the new guardian becomes active? When will that be.

My heart goes out to you. Two loved ones diagnosed with dementia this year! You don't need stress from any outside sources! Just detach from SIL as much as you can without starting WW3 -- that would be stressful, too!

I'm so sorry your dealing with two loved ones with cognitive problems. I've found that having a spouse with health issues is so different and challenging than a parent with health issues

Ignore the texts. Keep the calls short - phone battery dying is always a good out. Once the guardian is in place, you can breathe a bit easier since the guardian will be the person dealing with her "I want" list.

Emotional and physical energy is precious and finite - save it for yourself and DH. People like your SIL don't get it and never will, so don't waste energy explaining anything.

What is it about SILs? I dread my SIL's visits from out of town. She's hypercritical, but manages to do it in so indirectly that it's hard to respond without feeling like an idiot. ("Mama is soooo much better now that she's in assisted living and gets three good meals a day!" What? I didn't feed her?) My poor, long-suffering brother tries to compensate for her nastiness, but she know how to work around his good intentions. And at the same time, I'm not sure she's being intentionally critical or cruel! She may just be really dumb. (Not! There's a reason her kids moved two thousand miles away as soon as they both got out of college.)

Tell her what you think.....🤔
Hang up.....🙋
Say....
Good riddance.😝💃

This job is hard enough without direction from the peanut gallery! You're awesome for doing this for them 💖

Whoops. More on SIL. My husband was named first agent for health and finances to his mother. She was second. When MIL fell and it was determined that she couldn't make medical and financial decisions, SIL decided to step in and tell us what to do from another state.
She then showed up and decided to take over.
My husband has always cared and done things for his mother. After cancer and a stroke he has not been in the best of shape.
SIL decided that I needed to take care of MIL's finances and everything else because she didn't understand checkbooks or medical stuff, but she wanted to be IN CHARGE.

And BTW while Mom was in the nursing home, she'd clean out her Mom's apartment.
We said Mom isn't dead and she could come back home, so leave it all.
SIL decided she would still take over and stayed with MIL after she got home from rehab.
MIL and SIL just fought. SIL tried to boss her mom around.

I made an appointment with an elder attorney for my husband and SIL so they could figure out 'what exactly' their responsibilities were. SIL decided then that her mother was too much of a bother. She resigned as 2nd choice.
SIL left and said she was never coming back except to claim items she felt belonged to her.

My husband has since been dx'd with dementia and his task abilities are such that they want me to take care of his medical decisions and perhaps financial. We have all of that set up for us already and we have been working closely together since he had cancer.
SIL knows that my husband has a nice ring that she feels she should have. My husband's wishes are that he be buried with it.
SIL said that she 'gets the jewelry' that her mom has. I personally don't care. I have no idea how much it could be worth, but it looks like costume stuff to me.

Since there is no one to be appointed in my husbands place and he is not capable of making decisions regarding his own health care, I talked to a Social Worker and we started proceedings to appoint a Guardian for Mom. SIL was okay with that.

When the Guardianship goes through court, the Guardian has full transfer of her estate which is not much other than some really nice antiques and this jewelry. I imagine it will go to auction.

SIL automatically assumes that she will get what she wants. I read the papers and feel like once the court hearing is over, it is like she divorced her mom. She is mentioned in the hearing as being unwilling to act as POA Agent.
She calls me and texts me to tell me what I should be doing for her mother and also for her brother.

She said she wanted this ring. Very bizarre, she said I can display my husband in the coffin but she'd steal it before the lid was closed.
I
was
speechless.

What I am still doing. Taking both husband and MIL to appointments, hubby's appts are 90 miles one way to a VA facility. MIL's appts are here and there.
I have been advised by the VA to stop taking care of all of MIL's things as the rehab for my husband will take all of my time.

I also have a small farm with cattle and equine.
So.

I have known SIL for a long time. I always just try to let her talk in one ear and out the other.
But the 'steal the ring' floored me.

I don't think I am wrong in saying I am just about fed up.
Anyway, she is not reasonable and told me that SHE is so stressed because her mom and brother have problems.

I sadly smile and nod. She only deals with these problems by phone.

Just trying to understand why this is coming up at this juncture.
Is your husband’s jewelry heirlooms like from his father and thus her father? Does your husband have children? Wouldn’t that be a natural gift to his children?
I’m also confused as to why either of you automatically would assume inheritance based on guardianship?
Sounds wrong.
But I’m sure there is more to the story?
Edit: I would try to be kind to your SIL as long as her calls aren’t excessive.  This is her family. You can then hang up the phone and do as you please and feel better about yourself. 

Where is ur MIL? Still living alone? People can advise, but you don't have to follow thru on the suggestion.

Why do you feel by giving up SILs POA and giving guardianship to someone else means she can't inherit? The will determines inheritance Guardianship stops at death. The Executor then takes over and must follow whatever is in the will. Do u think Mom will ever need Medicaid. If so, her antiques will need to be sold for her care. And at top prices. Can't be sold to a relative for cheap. I would take any jewelry you think maybe worth anything and put in a safe deposit box and anything else maybe worth anything. If MIL is able to stay in her home, I would change the locks not giving SIL a key.