Maybe just maybe your niece is missing her GF and because of her illness she is thinking that if she is not around it's one less person watching her as it is my understanding of Anorexia that many sufferers push people away who try to help, sadly it can be loved ones that get pushed away first, as many sufferers of this illness try and do isolate themselves as much as they can, maybe this is what your niece is thinking/doing right now (one less person watching her) as atm sadly her illness is likely in control going by what you have said Hom3r
Your niece may be fed up with R telling the family stuff and while this was done with the very best intentions
I suspect your niece won't see it like this at all.