My bf and me have been in couple for 7 months, I grew up in a very poor family that could barely afford food, my boyfriend, him, grew up in a very rich family. Since we’re together I made him learn the value of money and not taking it for granted and he’s learning me how to accept gifts without thinking I have to pay back and to not worry about money. I started recently to talk to his sister because I wanted to get closer to his family, at first everything was going extremely well but then she started to act weirdly, always asking me questions about sex or talking about it in general even if I told her it bothered me, and I recently learned that she stole every gift my bf was supposed to gift me.

Context: my bf and me had multiple fights because he would tell me he sent me a gift and I would never receive anything so we thought everything was stolen by the mailman or lost and I told him to stop taking me gifts because it was getting lost so he was losing his money and I felt guilty about it

She admitted stealing everything after he put my gifts in the mailbox (before the mailman arrive) or directly stealing in his bedroom while he was away, she gave everything to her friends, sell them to have money to pay more stuff for herself, even said that she gave the phone he took me because mine is falling apart and I can’t afford a new one, to the friend of her mom because she was depressed (she knew that I have severe depression, severe anxiety and PTSD)

When I told her that I would get the police involved because she admitted stealing more than 100k (€) worth of stuff, she got mad and started to threaten me and my boyfriend saying she will kill him and tell him that I was cheating on him (I’m not and he know it) and lie to her family so they would hate me. I warned their grandma (the person who control this whole family) and showed her proof of what’s happening, now my sister in law is getting kicked out of the heritage because of how she acted, what she did and admitted doing (she also complained on “only” receiving 2000€ and a 5* hotel for her bday).

She now accuses me of ruining her life and saying that she was going to end herself because of me, we sent her at a hospital because she was starting to get physically violent and close to murder my bf, she admitted to the doctor that she was jealous of me because she considered me as “perfect” and that she wanted me to be with her and not her brother. The doctor found out that she have several physical trauma because of how much she is addicted to sex, and that since she refused to take her medication (she’s bipolar) she would’ve actually murder my bf if we didn’t react as fast as we did

AITA for denouncing her to her grandma and making her go in debt to repay everything she stole?