Not that obvious! Emily is an example. She cheated on the MC and that caused the break-up. There's also Lauren who gives her a second chance! I'm not even talking about other VNs, but this one in particular.
Most girls will not want a friendship after being cheated on, some can salvage a friendship especially if it started as one, but a few crazy ones like Emily you should stay away from. You can't assume all girls are the same or compare a whore to a faithful girl with morals.
Most stories, especially those in the romantic area, draw from real life experience. My advice is to go outside, get some sun, and meet some real people. Who knows, maybe even meet a real life girl. Because it is obvious to anyone who has interacted with the opposite sex and has had 1 or more girlfriends.