How to best deal with a difficult friend of my mother's?

Tell the woman that mom has incontinence of bowel. That just might take care of it, I know it would me.😉😣

Another option.

Call the friend and tell her Mum cannot go out, but you would like to have her over for lunch or coffee at Mum’s.

That will allow a supervised visit.

You tell her what you told us. That Mom has had a decline. That your experience in the past shows that this friend has left her on her own; that you feel this is no longer safe. That, therefore, the three of you can go on an outing when you have time to do so, say a lunch, but you can no longer allow her to take Mom out alone. That you are now the one responsible and you cannot risk it.
I doubt she will try to PHYSICALLY intervene, but it may be necessary to ask her to leave if she makes a scene. Should it escalate at all you can tell her that she will no longer be welcome to come to the house if she cannot maintain civil discussion and gentle manner, as this, too, would be upsetting to her good friend.
Dependent on her own level of mental impairment it will go one way or the other. It IS your home. And you are correct; you now are responsible TO and FOR your Mom.
When she is rude do the grey rock thing. Answer briefly and gently and repetitively with only the gentle facts. Do not argue. Do not defend. Do not explain.
Just as a side note you say SUDDEN decline. When was the last urine test? You know how we jump on this one here. A bladder infection can cause sudden, profound and unpleasant behavior changes.
Good luck. Update us how it goes for you.

I would think of your Mom and how she would feel if she was younger and sharper. This was a friendship she cultivated, that endured because (at least some of) your mom’s efforts. Support your mom in trying to continue what she started, do it for her, even if this lady isn’t your type.

Ask to tag along, just to keep your mom safe, Sit back, let your Mom’s friend take the lead in the conversation and be a “fly on the wall.” If they need something, help them up- jump up to get that napkin, drink refill, steady them when walking on uneven sidewalk, carry a heavy package. Let your Mom have a swan song experience. Let her safely feel some “independence” and a slice of her former life. You may find that your Mom is a bit sharper and happier after these visits.

My mom had a similar friend. I didn’t understand how they were so close. When I started spending time with that friend, I grew to realize why mom loved her. She loved mom deeply. After mom died she told me hundreds of stories that filled my grieving soul with new memories of mom.

Now I visit Mom’s friend when I am In Mom’s town. She now is a widow living in AL. She welcomes me, and hugs me, and shares her precious stories again.

If this lady abandoned your Mom, you would be upset about that. Think of her side, like you, she is probably grieving these changes and it is natural for her to be in denial.

Birchtree I would file this under that heading "more decisions I have to make for mom's own good." I completely understand your plight. My mother's friends have for the most part all passed but her core group, the ones who used to get together on a regular basis are still around and suffering from their own varying degrees of cognition. Her one friend would call weekly to beg me to take mom to her house even after I told her my mother hasn't left the house in 2 years. Then she would get on the phone with my mother and ask her if she could come which of course my mother would say yes. Then she would hang up and be upset because she didn't know how she could go, didn't want to leave, etc, etc, etc. I finally got to the point where I didn't let her talk to her anymore. Did I feel bad? Yes but it was better than my mother obsessing over it.

The moment I read "....doesn't stay with her the whole time.." I was out. If your mother "needs constant supervision" then she doesn't get to leave the house with anyone but you (or a professional caregiver) because you are the only one who truly gets what that means.

While it sounds like this woman has plenty of her own challenges that doesn't change the fact that your mother needs constant supervision and she won't be able to provide that.

If you feel like you absolutely have to have this woman in your mothers life, invite her to your house for lunch this way you will be there. Just know if she is this much of a bully she may say push the issue of taking your mom out while she is there for lunch. Just hold your ground.

Good luck to you, these situations are so hard. You're doing a great job.

WHOA! You know I read the summary before even reading that the FRIEND has COGNITIVE issues and I already had an issue with that friend. What a nightmare on wheels! So your mom gets distressed being abandoned in the big stores...gosh, doesn't that make us all remember losing mom when we were kids? And probably mom can't remember being scared/upset from the last adventure? IF she does, then she probably wouldn't want to go. My greatest fear is if your mom is left alone, that the friend could show up and take her! So my thoughts are, you're the one with the power/control as well you should be, i.e. you are POA and have legal authority. This boils down to friend taking mom against your consent being (am I being too dramatic or wrong legally?) abduction or kidnapping, which if I confirmed as accurate, I would not hesitate to inform this "Friend" of. If you ever see her and her vehicle again, I would note her car make/model and plate, just for safekeeping. I think I would inform the friend in advance and let her know you are POA and will not hesitate to call the police if she makes any attempts. Seems sadly like it is another episode of "no good deed goes unpunished." It was such a nice idea of you to put that call in for mom. Some days are so much harder than others to be a good daughter...

Maybe you could tell her that your mother is frightened in the big stores and she may wander off and get lost. So, she won't be going out with her anymore. You don;t have to totally shut her out, just certain things. She could come over to visit maybe. And you don't "just have to deal with it", she is your mother. You are concerned and have the right to be. Don't let this woman push you around.

Tell her NO and if she insists, call the police and have her "removed". Tell the facility that she is NOT to leave with your mother. If you have legal paperwork putting you in charge of your mother, the facility should have a copy of it for their records and that gives you leverage. If you don't, then you should contact a legal adviser and tell them of the situation and see if you can get the paperwork.

The friend said she has some cognitive problems...she may not be able to make good choices now. You r the POA. Your job is to protect ur Mom. Just tell the aide who the woman is and the car she drives. To make sure the screen door is locked so she can't barge in. All the aide needs to say is that its not possible that the woman visit. If the woman says she is there to take Mom out, she says that she has gotten no such instructions to that effect from family. That because of that, she can't release ur Mom to this woman's care. If the woman won't leave tell the aide she can call the police.

Morning: YOU are in charge of your Mom, and what you decide for your Mom, and who comes on your property.

Call the friend back and tell her she is not to come to your home for any reason, ever, and if she does, you will call the police, as she will be trespassing! If she does show up don’t answer door or converse - call the police.

Do you know BFF’s family? You may want to advise them what is going on.

You also should call the local PD and speak to an elder advocate. They can come to your home. They will also contact this friend. Your Mom’s BFF sounds like she has “issues” and may need serious intervention by both PD and her family.

Good luck and hang in there.