personally from what you say,i think it has been taken out of context.at 20 years of age to stop talkin over it,bit dramatic imo.,surely she should sit down with her mum like an adult and talk about it.
So it was out if context, she didn't call her fat. She said she's too fat to weigh X. Unless X is a very heavy weight, then it sounds like a blurted out poorly chosen comment rather than actually calling her daughter fat. And she's 20... She's hardly an impressionable teen. Sorry but it sounds to me like you've fallen for an Oscar performance here