I kinda hate this whole "you need to get over husband! I'll OVERWRITE him! I'll make you FORGET him!!!"
I feel like her problem was being bound by her promise instead of loving her husband.
They grew up together in a small village and started dating because they didn't know any better. Now she is wasting her life alone, sexually frustrated to the point she invents the whole "sex in exchange for defeat" thing to silence her guilty conscience and get laid. Her feelings to her husband weren't love, but just loyalty, and it's stupid, just as the MC said.
Even if she would solve the village's problem and left, she wouldn't be able to move on and find a new love. The MC's wording was forceful, but he was right nonetheless.