My boyfriend's bestfriend's girlfriend is crazy

My boyfriends friend is in a mentally abusive relationship with this girl, and things have gone way too far I just am so shocked.
They have had the police called for physical fighting. She got him falsely charged with child abuse. Their relationship is nothing short of toxic. We try telling him to just stop talking to her, that it's obvious she keeps him around because he provides for her and her child (she's only 20. Close to my age) . He doesn't listen. My boyfriend even moved out so his friend could move out of living with that girl. But he went back.
So anyway, what shocked me was yesterday I was scrolling on my Facebook and I come across this post he was tagged in. It was his girlfriend and she posted ultrasound photos of a baby. At first I was like "well, guess he made his life choice". Then today, I saw it again and realized she put the due date. If you backtrack the due date, you can figure out how far along she is. So according to math, she's about 9 weeks pregnant. The ultrasound photos she shared, the fetus is WAY too developed to be 9 weeks. It looks more like a 15-16 week pregnant ultrasound.
This wouldn't be the first time she faked a pregnancy. She did that once before with him, but to do it again and post ultrasound photos you probably found on the Internet and claiming they're yours is just....
I needed to rant because I can't believe someone would go THAT far. How do you not feel guilty lying that much? And I don't use the word "crazy" to describe someone often, but I have no other description for this.