How guilty should I feel for my break up?

A while back (August) my now ex partner and I got in a nasty fight that turned physical whilst on a snow trip. She was complaining of a sore ankle after a day on the slopes and worked herself into such a state about it that she refused to come from our room to dinner with the rest of the group. I instead had to serve her dinner in bed. Eventually annoyed at her behaviour I tried to leave and go and join the rest of the group but was met with insults and made to feel guilty for leaving so I stayed with her. However, the fight just got worse and turned nasty as we both devolved to insults and as tempers flared I got in her face to challenge her to repeat one of her more nasty insults. Somewhere in this exchange she punched me in the face and I reacted by grabbing her sore ankle. She was reduced to some form of panic attack so I got her some ice and water and sat at the other end of the room. From there things cooled down and eventually we went to bed together talked things out and all seemed forgiven.
Nothing more was ever said about the fight and our relationship continued as normal after that.

Around 6 weeks later, right before my birthday, during an innocuous petty argument she suddenly said she no longer wanted to continue the relationship. We spent the next few days together talking things out and essentially her reasoning boiled down to that one nasty fight as the sole reason she wanted to end things. She claimed to be struggling to deal with it as it weighed on her mind during other arguments etc and she claimed it had affected her significantly, resulting in nightmares and flashbacks. She even went as far as to say that she wouldn't change anything about us other than that one fight and the whole ordeal was very back and forth as to whether she wanted to stay or leave. She seemed genuinely confused and distraught about the prospect of us ending.
We left things on the premise of us taking some time a part to work things out. However I felt her became colder and distant over the next few weeks and communication came to an almost complete stop.

It was after this that I discovered that she was back with her ex, she had gotten back with him almost immediately and was in the process of moving in with him and as it turns out, had been talking to him and seeing him behind my back for a short time after our fight. Her attitude towards me was suddenly one of anger and hatred with claims that I was an abuser and she was afraid of me and false accusations being levelled against me. She had told other people that I pinned her by the throat, but admits to me she knows it's not true. Despite that, she refuses to admit to others that it's not true. She also seems to completely discount her hitting me as a relevant factor and has taken little responsibility for it.

Despite all of this, she maintains that she contacted her ex desperately seeking help after the fight and he was there to support her and somewhere in the process she fell back in love with him, but that she never would have contacted him or thought of leaving me if I hadn't been aggressive toward during the fight.

And this is where Im stuck. I feel extremely guilty for my actions that night and now I am having a very hard time letting go and moving forward because I feel responsible for everything that has happened and am stuck in a cycle of blaming myself for the breakup. I feel as though my actions during the fight led to or even caused her subsequent actions and it may not have happened had I just kept my cool. I even wonder whether my actions were so bad that what she's done is an equal and just response and possibly what I deserve.
Those close to me seem to think that she's the bad guy and that what she's done was inevitable regardless of anything I did but I can't seem to see it.
What do you guys think? Am I to blame for bringing this on myself? Are her actions an appropriate response or are they wrong? What would constitute an appropriate response to the situation?

As a side note, the only other time I've done anything remotely similar was to push her off me while she was attempting to drag me down a hallway after repeatedly asking her to let go. She still held that against me as though I'd been the aggressive one. She however has lashed out at me physically a few times. She apologised at the time but now she uses those instances as evidence of why she was right to leave me, claiming i made her act that way because I brought it out of her.

Also, the ex now bf again is not a guy from the past with whom she was friendly. They ended on extremely bad terms and she was with me within a week or two of breaking up with him because she claimed to have realised she didn't love him but had been harbouring deeper feelings for me from a previous encounter. A lot of our time was spent with her talking about how much she hated him and was glad to be rid of him and how much more she loved me. Now im the guy she hates and is glad to be rid of and apparently she's always just loved him more, go figure.

Quite a taleI know but....help?