Well, when thinking about breaking up, never take the other party into consideration. Obviously she will have to rent smaller, worse location etc etc. That's just life. She will figure it out.

2 things you need to think about:

1. If you're honest with yourself, do you want to break up or do you want to give it one more shot? Based on that question, you know what to do.

2. if it's the latter, think about what can possibly fix your feelings: did you fall out of love because of the cheating thing, or because you... just fell out of love as that can happen? Find the source of the issue, so you can work on it.

PS: honestly, I haven't been cheated on, so maybe I'm out of line here, but being bitter after 4 years, when she "only" kissed a guy and she confessed out of her own volition, that seems a bit extreme to me. Again, I can be wrong here and maybe cheating is cheating, no matter the 'gravity', but try to find inner peace with it, because how you are living emotionally right now, that's just not healthy.