Normally I find the use of swear words a bit unsuitable, but I think this is absolutely a case where the use of them is appropriate. The whole point is that she's fed up and she's snapping against her mother here, using ruder language than she normally would. (I haven't looked at the raw cos paywall and all that, but the context, her emotions, etc. all point towards this.)
Your "even if they did" remark is plain mistaken, she's literally been watching R-15 movies in every past chapter. Even with that aside, she goes to high school, there's no way she won't have heard other people use rude language.
Classifying the use of "fuck" as an error because "the japanese don't have an equivalent for it" is really missing something here. Japanese has various levels of formality (as I'm sure you who're so confident in your knowledge of Japanese are aware), and using one less formal than is expected in a social situation is rude. In such an emotional and climactic situation as this, it's obvious that the change in formality is intentional and significant, and the translation should get that difference across in English too. Now many people say that English doesn't have the difference in formality that Japanese does, but of course people speak differently with different levels of formality in different social contexts in English as well - this happens no matter what language you speak, it's a human social phenomenon. It's just that in English, there isn't a grammatical difference when speaking in different levels of formality, such as a different verb conjugation (like Japanese -desu, -masu) or noun declension (like Japanese o-, go-). Instead, formality is shown by the use of different vocabulary, e.g. more formal words like receive vs get. And swear words are a huge part of this of course, they instantly and clearly mark speech as being non-formal. Falling back on a rule like "using swear words when translating Japanese is wrong" is just a hindrance in situations where it really is appropriate.
Basically what I'm saying is that the use of "fuck" is a valid, and I would say probably the best, way of conveying the different register of formality that she uses in that scene. This is exactly the situation where she would direct them at her mother.