if you don't mind getting a used disk that might be scratched, gamefly's online store has mass effect for 19.99. i think they're also offering free shipping right now.
Get your daughter and get away from that situation. Spend the money on good legal council, I've been through the custody battles, it's worth every penny. I hope everything works out for you. And don't stress out on the old lady, the world is filled with semi-sane women who won't sneak around...