Best friend

Lately I’ve noticed that my best friend isn’t herself. She just got back together with her boyfriend (on and off for a few years) and it seems like she’s changed so much. She’s always mad, or upset about something and it’s almost always his fault. She doesn’t talk to me about anything anymore because her boyfriend hates me. He thinks that we are lesbians and we want to be together. All because i used the bathroom while she was in the shower. He’s super insecure and controlling and it sucks because we just moved in with each other. I can’t say anything to her because she just ignores me. What should i do?