I do that with mine, pop them in an old duvet cover on a 40 degree wash and then hang on the line to dry. A wash in the sink would do the trick if your mum definatley won't let you put in the washer. Maybe you could have a spare while the other is drying. Also have you thought of a cuddle pocket, bit like a sleeping bag for guineas, they may be easier to wash frequently. Hope this helps.