How do I tell my mom I want to get rid of our dog?

I have a blue pit bull terrier and she is a nice dog but she chews up everything, she doesn't obey, and she isn't even house trained and not to mention we've spent a ton of money on obedience schools and I have yet to see an improvement. I just can't do it anymore. Despite her multiple problems, everyone in my family adores her and probably wouldn't want to give her up for anything.