Why did my girlfriend break up with me?

She told about how she had fantasy dream about other guys, given they were movie stars, 4 nights in a row. I responded by saying thats not cool, because her drive with me really isnt all that good, once a week, maybe less, and we're 19. No, she's not cheating, but me saying thats not cool sent her off the deep end. She bombarded me saying how im an . I'm still confused, this is normal for her, she usually doesnt bother to listen to my opinion, only taking it as an insult to her own. For example, we once argued because I was minorly upset she danced with other guys while away for a weekend and had been drinking (when i say minorly, i mean i really only was upset for a max of 10 minutes). She was extremely mad when i was sad for a while because she may have moved to hawaii, i think that warrants momentary heart break. I feel like all I do is care about her, but she confuses me caring for her as something else, i dont even know what.