My friend I'm caring for (I'm her POA) ex-sister-in-laws come to the house without calling and try to remove her, can they, claim they can?

If they have a legal, legitimate POA then they can do a lot if your friend is not mentally competent. I would request a copy of the POA to ensure that it is indeed legal and not expired or ???

If she doesn't want them around, she needs to change her POA. She
has to be able to comprehend what she is signing and they should be notified in writing that they are no longer POA.

Lin521, assuming your POA is solidly legal and if your friend is legally incompetent, then, no, your friend's sisters-in-law can't take your friend out of the house without your permission. But if your friend's Alzheimer's dementia is "medium" as you say in your profile, then the sisters-in-law may be legally able to take your friend out if that person is willing.

In your profile you also said one of the sisters-in-law tried to push her way into the house, which is alarming, but I sense there is a long history that is causing these problems. So, if you think your friend is being endangered or even threatened by the sisters-in-law, I suggest you call adult protective services (APS) to find out if they are able to further investigate the situation and provide you some assistance before things get completely out-of-hand.

Kudos to you for providing your friend's care during this hard time. Best wishes to both of you.

Are you living with her or her with you?

I too would wonder what they are up to. Do they think brother left his estranged wife money? I gather that they were never close so why all of a sudden are they showing up unannounced.

If they were her sisters would be one thing but they really are not related so have no say I feel. Would your friend really have wanted them around? I feel that keeping them away is in the best interest of your friend. If your home, you definitely have the authority to keep them out. Keep the doors locked so they can not just walk in. If you need to open the door, make sure there's a storm door between u that's locked. Tell them "Sorry, this is not a good time. Please call before you come over." Then close the door.

I think they want her out of the house because they want to get her to assign POA to them. Was the house owned by friend and her estranged husband? Maybe they think they are due his half since her son is gone.

If she has dementia and you don't trust them, then don't allow them to take her anywhere without you. Tell them you are currently responsible for her and she can leave only if accompanied by you. That is your decision to make. They can, of course, apply for guardianship if they are family, and they may actually win it, but it will be costly for them to do this. They could be taking her to a lawyer, and we have heard of such things on Forum. Do understand that as POA you are a Fiduciary and are responsible to have meticulous records for any spending you do on behalf of your friend,and for safeguarding of her assets.