She's prolly moody because she is cheating on you and just keeping you around because you are useful. Whether or not she is cheating she is definitely using you, which means she doesn't respect you and probably will cheat on you. Nobody respects a doormat. Don't be one.

My suggestion, start treating her like a complete whore. Only talk to her when you want sex. Ignore her otherwise. When she calls say what you need to say and say goodbye. Then just hang up on her, preferably in mid-whine. Don't answer when she calls back repeatedly. If she continues to do so to annoy you, answer, lace into her for being a complete psycho, play on her insecurities, tell her she is a psycho and needs serious help and hang up again. Don't ever let her get a word in edgewise or suck you into a conversation.