She's already made it clear that she thinks Seb is going to fail his GCSEs and she seems perfectly happy with that. The only reason he has a tutor is because she gets paid to advertise it. In actual fact, he probably hasn't even had the tutoring, the only time she mentions it is when he's sat in front of the screen for an ad.
If you already think your child/stepchild is going to fail and it doesn't bother you, I guess going away during exam time seems an acceptable thing to do. Most parents want to be there to support their child as they navigate through the most important exams they've taken so far, but then most parents aren't selfish, self absorbed bastards.
Hopefully them bleeping off on holiday will be a blessing for Seb. He won't be filmed and snorted at every evening. He won't be asked how his exam went and laughed at if he doesn't think it did well He won't be mocked and belittled so often if they're off being selfish fuckers somewhere else. Hopefully either his grandmother or aunt will step up and support him. And hopefully some of the huns will realise that going away when your child has exams doesn't make you an inspiration, it makes you a complete and utter bleep.