AITA for leaving my girlfriend with the restaurant bill after her mother called me an impolite asshole?

We (27F and 25M) went to a restaurant. My girlfriend invited her mother. (60ish)<br><br>During the meal, the mother keeps making comments about how I don't live up to her expectations.<br><br>She made a comment about my (not-so-long) hair. "Why is your hair so long, can't you go to the hairdresser?"<br><br>I replied, "Why do you have a problem with the length of hair other men have? It's not as long as a woman's hair. My hair's fine. But thanks for the offer."<br><br>She said, "I don't like the food here, I want to order something else." I said, "We already ordered. Don't you think this food is good?"<br><br>She said, "It's not good, it tastes like dog shit! You're a poor boyfriend for bringing us to such a terrible restaurant."<br><br>I said, "Don't eat it then! Go to another restaurant whenever you want. You have enough money, you can go wherever you want. Why bring me here and complain?"<br><br>She said, "I'm leaving and I won't pay for this food. You two are impolite assholes and I'm not happy."<br><br>After she left, my girlfriend said, "You are a loser. I'm not paying for her, you have to pay for the food. It's your fault that she's angry."<br><br>I said, "It's not my fault! You have a bad mother and you refuse to admit it. I won't pay for her."<br><br>We had a fight and I left her there and went home.<br><br>She is furious and wrote me angry text messages.