Woa, I'm a mess right now, lesson learned, never read angst when you just woke up ==;
Imo the Bride confess to Fleur so they can both moving on fron their feelings, there's nothing cruel here.
Fleur can decline the friend's request to accompany her but she didn't because she wanted to fulfill her duty as a best friend! Fleur wanted to help her friend, even if she's in love with that friend and seeing the friend getting married to someone else hurts.
And this story comes from an Asian country so I can feel the Bride... It's cliché but it's the truth...