Housing benefit

My mum lives in a self contained annexe on the side of our property. She is 66, has no savings or other income.

She has been told she cannot claim any housing benefit to go towards the rent she pays me. Is this right when she could claim if she lived at the next door neighbours.

Is she likely to be entitled to claim any other benefits or alternatively could I claim any tax relief for supporting a dependent relative.

Thx

Jools