I'm not defending the way Isabelle speaks to her mum, but it does make make me wonder why she's so resentful towards her - there was a bit in the first or second episode where Eugenie was talking about her sons and her face lit up because she said something like, her son's always agreed with her and thought she was great whereas (I'm paraphrasing a bit), but Isabelle didn't (and then her face fell again as soon as she started talking about Isabelle). And that rang a few alarm bells for me
But I can definitely see both sides. And also, not that unusual that any parent and offspring would get irritated by each other in this situation