My elderly mother's hot water tap on her kitchen sink is very very loose and rotating and wobbling. She has individual taps for hot and cold. The sink is a stainless steel basin and the taps are supplied by flexi hose. I have managed to get my hand up the back of the underside of the basin and have established that the white hexagonal nut appears to have the threads stripped. It moves up the copper screw part of the tap but is really just pushing up therefore not tightening the tap. I can't see well enough to start disconnecting the water supply and replacing the nut and the sink is securely fitted and the worktops have uprights at the back so taking the sink out is not really an option, aside from which she has just had a severe heart attack and is recuperating slowly - she couldn't cope with the stress. Can anyone suggest a way to resolve the problem meanwhile?