Why did she want to break up with me?

Its more like, why did she wana break up with me. I am 18, she is 16. We dated for the past two months, then last night we broke up. She asked me to a dance two months ago and i said yes. I knew she really liked me. She even told me how cute she thought i was. After the dance we started going to movies and dating. We did stuff together, but didnt go all the way. One day i told her that like wasnt a strong enough word to say to her, so i said i loved her. she agreed. and she used to be really happy. There are couple reasons for her wanting to break up with me. She said yesterday that: She doesnt have the feelings she used to have for me anymore, and the fact that im two years older than her, and thats it. I dont understand how in one week she can just bluntly change her mind, especially after all the stuff we did. She said that she just see's me as a friend now. But after we had our conversation in person last night, I asked for one more kiss, and we made out for about 10 seconds. So idk. The thing is, i told her last night that we should stop seeing each other first, just because i sensed that it was coming to that. And she agreed, and told me that that's what she wanted to talk about with me. So yea thats about it, i still think it was a random thing to do. I asked her if there was another guy and she said no, and I dont think she would lie to me about that. But I have to get over this, I actually am, i just gotta act like i dont care, cause i cant thinnk about her anymore, it will cause me too much stress, Im 18 and im young, i dont need to be worring about some 16 year old girl. But to reiterate my question, why do you think she wanted to break up?