I was talking about another girl with my friend and my girlfriend read the texts?

Okay I was texting my friend and we were talking about this movie i did while being an extra, there is a really pretty girl in the movie and my friend was joking around saying "oh isnt she hot" and i was joking around just being a guy with my friend and said "oh yeah, shes really hot, i hungout with backstage" i was just joking and no i did not hangout with her but i also said a stupid thing like "oh she definatly wanted me" my girlfriend snuck my phone and went through the messages, i know i hurt her i wish i could take it back i told her how much i care about her and how much i love her and how i made a stupid mistake by saying it and didnt mean it, what should i do? Did i apologize the right way? What is she feeling? How can i make this better?