Her Ex- (Leo), genuinely loves her. And when she broke up with him, he thought its because he was shitty and unworthy. So he made up his mind to hone himself to perfection and then asking the MC to get back together.
at some point at a ball the ex asked MC to get back together, and the MC said she'll think about it. But the very next day, MC was caught making out with Zion and then MC said something along the line of "I thought about it, but I changed my mind". Ex is of course, heartbroken went crying and found by Juliana(a.k.a FL). Long story short, FL is kind enough to support Ex etc. And all that cliché shit. In the end, MC look back to FL and Ex think how Ex used to lean on her and stuff(kinda a dick ngl). But nevertheless, she went away and never bothered them.
This made me kinda mad, how MC had the balls do Ex like that. And the most infuriating of them all is Zion who just happens to be Ex's best friend. And despite him knowing Ex loves MC to death and cried a lot thinking about her, he still played pretend boyfriend with MC. They did Leo dirty, it's kinda sad for me :"
On a positive note, Zion and MC's interactions are really sweet and fluffy so go for it if it's your cup of tea.