What happened with my relationship?

So I was a sucker. I got with a girl not long after she had broken up with her ex of a year. Looking back I knew she was never 100% over him but we had a great time and they had had a very messy and destructive relationship, the complete opposite to ours.

We were together for 13 amazing months. I met all her family, we went on holiday multiple times, spent Christmas together and we constantly said how happy we were. All things she had never done with her ex. We just clicked on an emotional and mental level and she got really attached. She very much instigated building a future all the way to the end. A week before she left me she was speaking to me about moving in together. And begged me never to leave her.

I've discovered that her ex in the last two or three weeks of our relationship had contacted her saying he had changed. She was very open about it and showed me the texts, saying she had closure. Again I was a sucker I know. Anyway, fast forward a week and she leaves me. She blames the lack of passion, saying she wants him and that there was something missing. That she's confused if ever loved me. I knew it was because of him and sure enough she goes straight back to him. So I cut her out. Didn't bothered texting her. I delete her off Facebook and so she blocks me on Instagram an hour later.

She contacts me a week later, asking me not to reply, but apologised and said she was messed up and that she would always there for me because we were "best friends". That I deserved better and that I never deserved to be part of her self destruction. She starts liking all these posts on social media like "it's dangerous talking to someone every day, because when they are gone it's the loneliest place in the world" and starts stalking my posts. So again I don't contact her at all despite the urge because I need to heal.

She then contacts me again a week later saying she was sorry for things she had said. That she didn't mean it all. That I was always her most favourite person on the planet and loved me and always will. That she now felt empty and that every time I was with her she felt whole. That she felt so sad not being with me that it hurt. That the time we were together was the happiest, most fun, most loved she'd ever had. She wrote that she hadn't left me for him (lie) but for herself. But that she didn't like being so intermingled and attached to me and that she wanted to be more independent, and that she didn't want to be in each other's pockets. She felt herself for the first time in a while and one day she might regret the decision but she was happy.

I know I was a rebound but can anyone make sense of the situation? Was it the whole thinking about commitment that freaked her out? I know she was never over him completely, but was her ex an easier option? Because I knew it was more a physical relationship than anything which gave her the lack of real attachment. Are there hints of GIGS in her going back to her ex? Her parents went through a very messy divorce and she said she didn't want to end up like them. Could a broken home have played a part?

She's just changed her reasons for leaving me so many times. I know we will never get back together but I need some sort of closure. It's easy to put it down to being a rebound, but it was a year not one or two months and she was honestly really happy. There was no indication she was going to leave and why the heck does she keep texting me? She's started posting snapchats she never used to because it's the only site I now follow her on. Does she just need the attention?