I really enjoy the leads interaction, they're quite cute.
This new girl though, looks like she's being set to be the rival/villainess. I'm hoping it will end up being a misunderstanding and she's not actually trying to flirt with him but I kinda doubt it. I think it'll more likely play out that A. her relationship with current bf isn't going how she'd like so she's getting nostalgic for her old relationship and is hoping to get back together or B. having a rough patch with bf or feeling neglected so she's trying to make him jealous. Either way though would be selfish and immature. She really should either work things out with her current bf or break up with him. Trying to start something with an ex that she's already lucky is still her friend given the circumstances of their breakup while still dating the friend she dumped him for - that's just begging for a stupid mess.