she never loved the hero. Firstly: Recent chapters pointed out that Irene told Yuno that she lost her virginity to him, chrome obviously knew that she was lying to him as he was the one who did her first in the group. Secondly: she cheated on him MUCH MORE than she cheated on Chrome.
Would you do these things to a loved one? I wouldn't think so. The bitch MIGHT'VE (unlikely) loved Chrome first, but her ambition got the better of her and thought that in order for her to reach the top, the hero would be her best ticket to get up there. She went with THAT and THAT only.
She doesn't regret her actions and I'm convinced that iff she could do things over, she would do the same things she did back then.
Her thoughts, moments before her ensalvement:
"[That was cheap if my life is saved]
[I'll lower my head as much as needed]
[If you are going to violate me, please do as much as you want]" (don't mind the bad translation, he/she's doing his/her best). It shows us that she would do ANYTHING for her own survival, she literally doesn't mind another man violating her, all the while engaged to Yuno. She cried, not for a fact that her fate is now sealed as a demon hunter, but because of the fact that her body metamorphosed to a demon.