It would have been nice for her to wait two days and I would have thought relatively easy to do during exams at this age.
However maybe she blurted sooner then she intended, may be she has other things going on, maybe she was coming under pressure to end it form her parents ,new guy or events needing to attend as a couple needing numbers. Maybe she was just selfish and unthinking, maybe she a drama lama maybe she was stressed and it was the best thing for her to end it now or maybe she thought being straight was the best thing.
I don’t know and I don’t see why the OP or her son needs to focus on the girls reasons.
It’s done – OP needs to get her son focused on his exams. A fuck you I’m going to do well despite all this attitude – could be an advantage there if he can reach it.
I have a DS and two DD. If anyone had done this to them just before an exam I’d be livid – whatever their reasoning.
Though if they were the one doing the dumping I’d want them to be considerate but not to the point that they were suffering any ill effects – even if that meant dumping someone just before their exams.
Highly hypocritical – while I like to avoid hurting others and encourage my DC to be considerate to others- my priority is my DC at least until they are adults.
I also think there is a difference between waiting a few days especially when you can avoid other party and waiting weeks, months years at your own expense of health or happiness and I'm not convinced by the slippery slope argument that first will lead to the second - it's more complex than that.