@TheKuudereDude These Isekai/Fantasy are basically characters in RPG worlds... sometimes it's quite looser than others... but it's pretty much influenced by dragon quest. Like how every fantasy story is influenced by Lord of the Rings (though I think Dragon Quest might have also had some LotR influence).
--------
@john9983 Tsundere is forgivable for close friends or minor matters not meant to be taken seriously... but this wasn't her being tsundere... this was her being a brat... she doesn't even have a single reason to give why he should rejoin them... but wants him to be there... she could just leave the party if she wished, but she won't do that...
though at the same time, there is the understanding that he's the weak link in the party. She honestly believed that. So that's why him being kicked out can't be wrong from her perspective. I mean, our MC got his cheat AFTER he was kicked out... and her journey is about saving the world after all...