Love is a complex emotipn built from other emotions. You take one or two things it starts to dwindle. She felt jealous because she loved him and didn't want him to be taken away from her. She felt regret because she felt her friends' love lives were better than hers. Take away Jealousy, and she felt no need or want to keep her fiances attention. Take away regret and she had no comparisons to make her love life feel special. I believe she truly does love her fiance, its just he steps to make her happier with her love caused it to fall apart, thus feeling practically nothing for her fiance.