It's the way she the actress talks - every s and t over-enunciated. Does anyone, especially a 20 year old, talk like that?
As for her brattishness, she's got a point about if she was at some uni 'away' her mum wouldn't have a clue what she was doing every minute, but..... she's at a local uni, which she chose, so she could still live at home and work on the farm (thought it was weird when she applied - I couldn't leave home for uni fast enough). What does she expect? I wish she'd just bog off, she's behaving like a 14 year old!