The Nile is not only a river in Egypt...
Anyway, if this was reality, she would have lost him forever and the other girl ("Ennochi") would be the one becoming his girlfriend. But it's a manga, so the goal is: "Let's find the most toxic relationship possible by creating the most incompatible characters and try to give off the idea that it could somehow work."
And then the readers somehow think that no matter who you are and how you behave, you could get that big, nice booty, the "prettiest girl" around. Yeah, maybe, but chances are abysmally low, so do not even try.