Why had she changed her mind so many times??

I was seeing a girl for just over 12 months, and i wont lie we did have a few problems but these were surpassed with all the good times we had. Anyhow two weeks we went away for a couple of days for valentines day, and at that point we had decided to go as friends as she said that she still had feelings for her ex-husband. Anyway within an hour of getting to the hotel she was being very loving if you know what i mean (without going into detail) and we had a good night, nice meal, and a good talk. During that first night she said that she was confused about her feelings, but at the same she didnt want to loose me. The next day (valentines day) we went a walk and she explained why she had been feeling like she had. Apparently she missed having a father there 24/7 for her two children, at which point i said i understand, and i would love to be there for all 3 of them. Then she told me she was over him and wanted a future with me, and would like to eventually get married, maybe abroad. That day and night was perfect in every way, i felt that we had got our spark back. When we got back home, everything was again good. And she would text me to say she wanted me and loved me, and kept talking about where and when we could get married. This continued for another week, then she went out with her work friends one friday night for her works leaving do. When she came back late that night, she wanted to make love to me, and again eveything seemed perfect. The next morning, she obviously had a hangover, so i took care of her children so she could rest before she went to work. Again everything seemed fine, and she was due to stay at my house that night, while her ex-husband had her children for the weekend. That night when she got to my house she seemed a little funny, and when i asked her if there was anything she said no and that she thought everything was fine between us, so i left it at that. The next morning (Sunday) again she seemed a bit funny, but i didnt say anything for fear of annoying her. Anyway i was due to go up to her house that evening, but before she left my house, she said that she wanted to be alone that night, as she had to prepare for her new job that started the next day. I said that was ok, and that i expected her to say that. She did however say that she really wanted to see me the next night (monday) Anyway Monday morning and she phoned me before she started her new job, i told her she nothing to worry about, and that she would be fine. She told me she would phone me when she finished. At this point i still thought i would be going to see her that night. When she called, she told me about her first day, then said that she had some reading to do, and that she wanted to be alone that night too, again i said fine, but that i would miss her alot. She phoned me that night and we talked for a while, but i didnt mention my feelings. However i texted her later on and asked her if she was having second thoughts about us, at which point she say she just had a headache. The next day (tuesday) she phoned me again before she started work, and i said to her phone me when you finish. All through that day my mind was racing, thinking something wasnt right. So i texted her again asking if there was something up, and that she should tell me when she wants to see me again. Then about 4 hours later i got a text back, stating that she tried to love me but she couldnt anymore, and she wasnt in love with me. My heart sank, even though i expected it. What i cant understand is why did she say and act like she did only a few days before and then suddenly change. And im more annoyed that she didnt tell me to my face or at least talk to me over the phone. Since then i have sent her a bunch of flowers telling her i love her, as well as texts asking for a explanation. But all i get back are nasty texts, saying stay away its over, get over it, etc. To be honest she has been finishing with me one and off for the last 3-4 months, but everytime she wanted me back. But this time it is over. I dont know what to do, as she has really messed with my mind, and its effecting my social life and work. Can anyone shed any light into why someone would act like like this?