This is a bit of a long story, so I will attempt to be concise. My sister ("Sandra") and I grew up in a very abusive household. I became estranged from the family and she went into foster care when she was very young. After 8 years of separation, we reconnected and at first things were really good. I introduced Sandra to a few of my friends, including "Mog" (M27) who she later decided to start dating. She would spend all of her time with Mog and after Sandra started living in our house, Mog was at the house all of the time. I would say 4 out of 7 days of the week, he was there. He would leave the place in a state and he would break some of my/my bf's stuff (and never offer to replace or pay for the damage). This included a gaming PC that my bf had for over 10 years. I tried to talk to Sandra about this and asked her if Mog could come around less frequently or if they could meet up outside/another location every so often because he was using all of our stuff and not contributing. Sandra texted Mog about this immediately and she became very quickly upset. She said that it's her house too and she didn't want to be dictated to in her own house. So she continued to invite Mog and I would refuse to spend time with him around because he was disrespecting our house and wouldn't budge on this. There was a lot of arguing/avoidance during this time. After a few weeks, Sandra said she was being isolated in her own home and decided to leave our house without any notice. She just sent me a text while I was at work that she would be gone before I got back. She said she would never speak to me again. Sandra calls every 6 months or so and asks (without saying anything else) if I've forgiven Mog. Every time, I say no because he didn't apologise or even acknowledge what he did. AITA for letting her leave and not building a relationship with her? Sometimes I feel really mad/sad about the whole thing, but other times I feel like I was right to protect my boundaries. Happy to provide more info where requested.