Can we please move on from her? She shouldve been gone by like chapter 10 or something
If she wasn't actually FMC's twin sister, then cutting ties with her may be easier, but unfortunately, that is the case here. Even if he wants to avoid her, especially if FMC wanted to patch things up and get back on good terms, then he'll likely see her more often than normal exes would want.
Don't know where they stand in finally putting their pasts behind them and moving on, but if he wants FMC to be happy, then he's gonna have to be on not-awkward, at the very least casual terms with her sister.
If the MC were anybody else, I wouldn't blame them breaking up with her
much earlier on in the story, but we're here for the long haul.