estranged child of EU worker and right to claim IS if in full time education

can anyone point me to the case law on this issue?

i have a student who will shortly turn 18 and is the brazilian child of an EEA worker but is estranged from him. currently in care but the application to discharge is going to be sucessful as mum is in brazil and wants child back.

child is in full time education as i am sure is able to claim IS & Hb in her own right as she remains in education and has retained right of residence (actually she has a current right of residence which has not yet expired)

but i cant remember the case law and we need to get her claims assessed rapidly as soon as she turns 18 so she can stay here independently for the coming period.  she can claim portugese citizenship but this is not as good for her actually ..
thanks