My girlfriend gave me up for some other guy?

me and my girlfriend dated for 3.5 years and when graduated she got this grup of freinds and thier was this guy thier who was giving her alot of attention and she liked it. I wasn't the best boyfriend ethier there was some verbal abuse and twice physical abuse. i didn't want her to have friends because i was afraid of her cheating. anyways she broke up with me and 3hours later was sleeping with him and continued a relationship with him and still having with him. Then 2 months later she an i got back together and been together 5 years since. She says she didn't leave me to be with him and she still wanted to be with me and loved me but didn't think i would want her after sleeping with him but she never tried to tell me, she actually put restraning order against me and continued to see him. she also says she never liked him like that and when she left he did nothing wrong but she just didn't wnat to be their anymore, and he was nothing, to her. what do youi guys think did she want him and leave me for him because she thought he was better and did he possible show her that he didn't want her and then she jsut tried to get me back or was it all becasue she loved me and the reason she came back or do you think i got suckered back in and shes waiting for someone better that she will like this time becasue she did complain that he sucked in bed and he was ugly. my other question is that how could somebody that has touched antoher person so long jsut be able to touch somebody so soon after because i tried and i hated my self for it when we were broken up and she just kept doing it and didnt feel bad. is thier something mentally wrong with that person i think so