So many people on here that think there is nothing to forgive. Actually that’s 100% debatable. If she’s asking forgive as in forgiving a wrong doing he has done against her- the situation will reveal whether she feels he has wronged her. If he left her, went off despite all her pleas for resolution, and then went and shagged someone else, he made that choice rather than to resolve their relationship, at that point he decided what was more important to him, and if he now has decided to come back and work at it, he should be sorry for the dent he put it the trust between them, in choosing someone else over her, and the mental struggle she has thinking of him with someone else.
if she ended it with him or it was mutually ended and they were happy to go their seperate ways then she wouldn’t have anything to forgive him for BUT, in terms of getting back into a relationship, what’s the actual point? If it is really love, our heads are full of that person, no way would we want to lie entwined naked with someone else, and if he could quickly and swiftly do that, I really wouldn’t bother with a relationship moving forward, it’s totally pointless. I personally wouldn’t be able to cope with it in either scenario, it would just tell me that he and I were not meant to be. I would never move on with some other guy, in any way, unless I was fully over, never to return to my ex and feeling a lot for the person I got involved with. People can decide for themselves what they find forgiveable etc, we all have our own boundaries