@kar98 Let's see
If a boy and girl were in love, can they be friends??
We should approach the answer from two perspectives
Girls perspective:
In general, girls are more emotional at the same time, girls heal quickly and move on.
So if a girl says let's be friends, then she means it. She can get over you after her marriage completely. She might feel guilty sometimes if she feels that you are suffering but in the end, after getting married she won't have any time to think about you. So she will be just fine and will be happy with her husband. Girls know how to be happy better than boys.
Boys perspective:
In general, boys are less emotional but if a boy gets wounded, initially he might feel ok but he will start feeling the pain later on, boys cannot heal quickly, it takes time and boys have self-destructive tendencies. They either become silent or violent while going through this lane of pain. Boys can say ok to friendship and may act as a friend but can never see the girl as their friend. Although she gets married, he longs for her. He might not say it or show it but it can be seen via his actions, here and there. So it will be a suffering to him. And yep, he might long for her body too. Having said that, I don't think it is because he is after her body or lustful (at least not always), it might be just the case that he wants to feel her love completely and sex is one of the best ways to express love. So he might want to have sex with her to feel her love, not out of lust or revenge. But if he really loves her, he will understand that she is married and respects her relationship with her husband and he will stay away although it is painful for him.
Bottom line: Yes, a guy can be a friend to the girl but can never see her as his friend, he secretly keeps loving her. But it always better to avoid friendship and cut ties with her altogether. As it always hurts to see someone you love so much with someone else (both for boys and girls). It creates confusion inside you as you love her and want to be with her but at the same time you also want her to be happy with her husband. Both ideas conflict with each other, so it pushes you into an endless battle and suffering. Either you lose the expectation of being loved by her or lose her.