**UPDATE** TO I DON'T KNOW HOW I FEEL

Here's how I would feel, I think.

She is ill. In her illness she perceives that you hurt her. There's no way to explore how she thinks you hurt her since she won't talk to you. Unless some other mutual acquaintance or relative has more information.

By going to see her, you made it clear you care. It's all you can do.

There's nothing more to do at this point.

There have been cases where perfectly respectable teachers became promiscuous due to brain tumors. Behavior can change abruptly and with no explanation.

Since you love her, of course you are hurt, due to both her illness and her rejection.

There is at this point nothing you can do for her except pray.

This link explains how and why brain tumors cause behavioral change.

https://moffitt.org/cancers/brain-tumor/symptoms/mood-changes/

the mass on her brain MAY be the reason for the irrational behavior.

look at what she has done 1) turned on your (assuming that this is recent) and 2) checking herself out of the hospital.

again, assuming you aren't a horrible human being - she's in need of someone to help her - may not be you though.

another family member may need to see if they can become their legal conservator and perhaps even make her get the surgery - if the surgery is going to make the problem go away.

or..just accept this as one of life's horrible kicks in the teeth to both you and your sister.

I hope your sister is doing better. I know your relationship has been strained the last couple of years and I know that she has treated you terribly for no apparent reasons. But I also know that you never wanted anything like this to happen. I will pray for her and your family. Call me if you need anything or if you just need to talk.

When the brain is affected often so is the personality. Pray for peace for your sister. She is going through a lot.