You will have to completely ignore what she says. I agree with Dandy, when you EXPECT them to try and smear you, it's a lot easier. I found out pretty quickly who my true friends were. And, blood will ALWAYS be thicker than water. Which means her family will 100% side with her and also make you out to be the bad guy.
As Hawkeye said, she is the one who drove drunk w/your child in the car. Enough said.
I am really proud of you. You are going through a hard time, but protecting your child, which is the most important thing you can do.