This is all were being told by OP, far too often teenage girls are being made out to be 'crazy or jealous' when the boyfriends are horrible and cheat and then the parents do nothing about it and think he is the light of their lives.
I'm sorry if you've been hurt by a situation similar to what you've described but you seem to be projecting onto the OP. There's no obvious reason to doubt what she's written from an objective viewpoint.
@TedsTortoise
This is a tough lesson for your son. Obviously he cares about his girlfriend's wellbeing enough to not want to hurt her feelings, even if he doesn't want a romantic relationship with her any longer, which shows he's a decent young man.
But this is one of those pivotal moments in life where he learns first-hand about what it means for a person to be responsible for their own feelings.
He knows he doesn't want to continue his romantic relationship with this girl for whatever (usually complex) reasons, so being responsible for his own feelings means he has a responsibility to communicate that truth to her in a clear and kind way.
He doesn't have to justify his feelings (as in prove their rightness or wrongness) to anyone, including her –feelings are not facts, they are personal – though he may decide it would be right to give her some kind of explanation for why his feelings have changed, even if that explanation is difficult for her to hear (eg. "I do care about you and enjoy spending time with you, but I have other people in my life besides you, like my friends and you seem unwilling to accept that so being in a relationship with you isn't working for me" - or whatever explanation is true for him).
She then might have a lot of difficult feelings in response to hearing what he has to say –sadness, disappointment, fear of loss of control over the direction of her life. And those are HER feelings to deal with in a responsible way. It may take some time for her to get through those feelings. But they're HER feelings and it's her choice what actions she takes in response – healthy or unhealthy.
Some people will go out and get drunk and vent and cry to their friends. Some people will hide in their rooms and eat ice cream and think about what went wrong and how they might act differently in future relationships. Taylor Swift writes songs and makes a lot of money. Some people go to the gym a lot and tell themselves they'll find someone better. A very few people will kill themselves and that is sad because it signifies extreme mental health issues and a real lack of coping skills. Those are still that person's choices alone, and nobody else's.
Your son might also have his own feelings to deal with after he's broken up with his girlfriend. He might feel guilty about the bad feelings she's having but recognise he can't 'fix' those bad feelings unless he ignores his own feelings. He might feel relieved to be free again. He might feel confused. And he will make his own choices about what he does afterwards. He might go out with his mates and get drunk and try to ignore the guilt until it fades (which it will). He might have a quiet few days remembering the good times and feeling sad himself but also reflecting on what sort of different qualities he might look for in a girlfriend in future (eg more sociable herself and not wanting to spend all her time with him). He might race out and rush into meeting someone new without thinking too much about it all in which case he might find himself in a similar situation down the line. Again, all his own choices. All you can do as a parent is acknowledge his feelings, offer him wisdom on what sort of responses might be healthy ways of dealing with them and what might be less healthy, and let him choose.
The girlfriend's parents sound problematic given they berated him for not feeling the way about their daughter that they wanted him to (as though she/they own his feelings, and not him!), so it's no mystery where her control issues and poor ability to manage her feelings in a healthy way come from. Hopefully he can see that if it's explained to him.