Yeah, but I think you underlie my point as well. Women are generally a scarce resource for the average man. Males don't have women approaching them constantly and throwing themselves at their feet. Women do, and generally are jumping into a relationship, or into bed, or into the hypothetical arms of a sympathetic guy friend upon relationships not only ending, but even hitting the rocks. This for one thing primes them for potential to "cheat" like ham's girl. Not to use him as an exact example since I don't know details, but theoretically she could be seeking solace from their fight and the "cheating" happens when she gives another male an opening by going to him during a rough spot with ham.
The thing about oxytocin is that like any other neurological chemical reaction you can get tolerant to it. So the same partner might create smaller and smaller doses of it firing in your brain. Whereas the novelty of a new partner is going to boost the oxytocin reaction up again and give you back that pair bonding high you are now missing with old Sally/Sammy plain and boring. The sooner you replace that oxytocin the easier it is to break free of the old bond.
For a guy you have to push through the depression you experience from the oxytocin withdrawal, and go be proactive to replace it. For a girl, sure you may be sad, but as soon as your girlfriends get you out to the club there will be multiple new partners showing up almost literally at your feet to replace your missing chemical. Due to cognitive associations from prior hook ups or first dates, that stuff starts flowing again immediately
even if she isn't interested in going home with the guy.
For the dumped boyfriend on the other hand, even if you go try to jump back on the horse the first rejection will feel twice as bad in your chemical starved brain and limit your ability to bounce back. Thus we see guys being stuck on that "one" girl and trying to string a ruined relationship on past the point of no return even while the girl is going out with a new man.
I'm really just talking out of my ass, so that could all be somehow proven wrong, but it sounds good.