there are enough red flags here , but she was honest about it. Why not help her getting over her ex ... and maybe land in a good relationship.
sometimes things that don't make sense at all can work out well , yes it takes more energy and patience and the risk is higher - like i've said if you are doing exams and you cannot have anything else on your mind you should dump her or temporarily cutting off. Guys who give simplified answers probably focus on one thing only --- cheating --- , like different forms of love you have different forms of ''cheating''. If it was neurotic or obsessive she would probably lie about it but she didn't.

If you have enough knowledge about humans in general or a very good relationship with yourself you can deal with this , i can deal with this and many people can - the people that tell you to dump her without explaining just don't want to deal with this out of lack of self-knowledge or lack of understanding human behaviour in general and not to mension the fact that some people really got hurt by previous relationship thus making their opinions very rigid.

there is not such thing as a bad relationship , there are relationships which require more effort and more patience. It's all subjective and based on personal values, people do stupid shit and are dickheads too often but at the end we all forgive eachother.

1. your ego can't stand the fact that she cheated
2. signals show that the person in question can't have a healthy relationship.

alot of good people on this forum but some of them probably cheated once or twice as well - and some of those are telling you to dump her ass while they themselfs probably did get a second chance.
personally .... i would dump her gently because i have too many things going right now and i don't have time for it..... do you have enough time ?