Anonymous wrote:OP you have had excellent advice in terms of welfare checks etc.
My instinct would be possibly to sign the property over to her, and be done with it. But then I'm harsh and a bit cut and run.
This sounds like an easy solution, but having done this in my own family, I can tell you that it can backfire badly. A sibling and I owned a house and we gave it to another sibling who had been living there. Shortly thereafter, he stopped paying taxes, etc. and the house went into foreclosure. Also there was disrepair. Long story short, he moved out and we are still taking care of him. Fortunately not much of the burden falls on me.
OP, some thoughts I had after reading are these. You are never going to sell that house. Your sister and her friend are never going to let anyone in and if they do, it won't matter because the house likely will require so much work to make it livable (sewer back ups and hoarding are two things you mentioned) that no one will want it.
You are probably going to have to evict your sister and her friend if you want them out of the house. You are the trustee of the house, but you haven't said what the trust says so you may or may not have the right to do that. But even if you do, you are going to spend a fortune in legal fees and time to get her out and then another fortune to get the house sale ready.
Your sister's friend sounds like someone you should consider a blessing. It sounds like your sister has her own mental health issues and now she has someone taking care of her. If she didn't, that would be yet another problem that would likely fall on your plate since your sister can't take care of herself. You have to take the good with the bad.
You asked about cutting your sister off. I know for me, I've had to set boundaries and once I did, the asks became fewer. But, if there are actual needs, it is really hard to say no if you can solve problems with money you can afford to pay.