Do find out how much money your mother is entitled to by law to help with the fees, Panorama had 2 programmes on recently showing how social workers were saying no money was available when some or all of the fees had to be met by social services, regardless of any assets. Social workers should do some sort of assessment and pay for the nursing part of the fees, find the BBC panorama web site, and there are Ombusmans decisions, for some further help.
Like Ethel says find out your rights and don't let anyone stop you getting any help you may be entitled to with the fees