Is it reasonable that she fell out of love with me so quickly?

I was in a relationship with a girl for about 11 months. It was an up and down relationship but we had some real high points. In our 9th & 10th month together we started saying I love you and talking about the future together in a partly serious way (moving in, having kids). It felt like we turned a corner. We got into a big fight and then she became in her words "indifferent." The fight started because was being bitchy, put me down, and said a few hurtful things so I got frustrated, exasperated and yelled. I said sometimes she made me feel like a "f'ing idiot." Once we cooled down I immediately and genuinely apologized and tried to make things work. She said no one has ever talked to her that way, but also told me a previous boyfriend hit her. (?) She also was abused when she was young. She fell out of love so quickly and did not put in the same about forgiving and moving on. She didn't even really care to hang out anymore. How can someone who is in love fall out of it so quickly? I know she has issues with trust and intimacy, but I still feel like she sabotaged or threw our relationship away. We broke up about a month ago, no personal contact since. I'm in depression.
Is it reasonable that she fell out of love with me so quickly?
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