Holy wow! What a mom. Anyways, I am so glad that you care about your friend like this, to be concerned that her mother is oppressing her, because she is.

But you guys are in 6th grade? Don't worry, most people at this age can't really confront their parents on a mature, adult-to-adult level and hope to win anything. That time will come though, when Audrey realizes that she doesn't want to live under her mother's teat for the rest of her life, and stops taking the crap. When that time comes, she'll probably talk to you about it and you can help her out then. My parents are pretty cool, but I imagine I'd be terrified of confronting my mother if she'd raised me like that. So yeah, just work with what you guys have now in terms of friendship, and show her she can trust you as a friend, no matter how her mother doesn't like you using the word "heck." Anyone can tell when someone is making an effort to be a good person, so be nice and helpful when possible and it all should work out as you guys grow up.