He didn't have to love her to feel guilty or realize he screwed up a good thing. That's just common sense. They were friends, great friends and he used those good feelings to have sex with her simply because she was girl. It took changing and fatally damaging their relationship for him to recognize what they had was what he truly valued. All because he was stupid enough to believe that having positive and genuine feelings for someone of the opposite sex means you have to have sex. He was an idiot and she was naiive.
Men like to pick up and pretend nothing happened so I wouldn't be surprised if the pair in real life are still friendly. If she forgave him and saw her own folly in the situation and pegged him for the chauvinist idiot he is, they may have been able to see each other every now and again with no problems. She was portrayed as a regular chill but impressionable girl, so I could see her "letting it go." But I doubt they'd be bffs though. In a perfect world, he'd feel fairly guilty and sheepish around her if he was ever truly remorseful. However, they were both adults who had some pretty warped, immature thinking about relationships.