I think I'm going to leave my girlfriend after she faked a miscarriage.
Is the fake miscarriage something you can't get past?
It feels bad being with her, I don't want to be part of that family
I understand your frustration, faking a miscarriage is a horrible thing to do and your girlfriend is definitely in the wrong. Her lying about something as serious as a miscarriage is hurtful to you.
I don't know what to do.
What are you do is up to you, but it's OK if you want to end the relationship with her. Lying to you about a miscarriage was quite cruel and it's understandable to not want to remain in a relationship with her.