What may possibly be going on here (purely speculating) is that the woman was heavily invested in this bloke (emotionally) so there was a part of her that really wanted to be with him. He however abused her trust (by cheating?) and in so doing caused her a great deal of hurt. Because of how much he meant to her she found a way to forgive him and to try again but there was a part of her that was wary. Over time she found herself fighting a battle btw what she felt and what she thought. Btw what her heart wanted and what her head and experience told her she needed to do. For her heart wanted to be with him, wanted to believe him, but her common sense and experience were telling her that he didnt really care about her and that he would probably hurt her again, would probably betray her trust once again.
The thing is that trust isnt something you can simply manufacture, and once lost it is very difficult to regain (cheaters dont seem to accept this simple reality). When she asked him if he dreamt of his ex i think she believed she knew what the answer was but she needed to hear it from him. When his answer was not what she believed was the truth she suddenly realised that try as she might she just couldnt trust him. Realising this she broke things off. I dont think his answer was the straw that broke the camels back and i dont think she broke up with him because she felt he was lying per se. I think she broke up with him because in the moment he gave the answer she realised that she just couldn trust him...Yet still her heart is giving her some cause to doubt her decision to break up with him.
And this is what i believe is the reason for her question. Asking us if she has done the right thing, for there is still that battle going on btw her head and her heart. Her head knows she has done the right thing though the strength of her heart creates some doubt. I believe this topic of her's is an attempt to combat the doubt.
Personally, from what i have read i think she made the only decision she could. She doesnt trust him, he doesnt appear to genuinely care about her. The recipe for a truly toxic relationship.
In a relationship (no matter how much you care about the other person) if there is simply more hurt and unhappinness than there is joy and happinness then its usually best to move on.
“The quickest way to rectify that mistake (choosing the wrong person) is by learning from that, moving on, and choosing much more wisely in the future.”
“When we are in love, we are convinced nobody else will do. But as time goes, others do do, and often do do, much much better.”