I'm studying again at the moment (at the grand old age of 37, and entirely self-funded) and I have to say that I think it's worthwhile (obviously, else I wouldn't do it). It keeps the brain from atrophying, enables me to get experience in something new, is a chance to meet some new people and remind myself of how incredibly young everyone is at 19!
I think that if a pensioner studying stopped a 19 year old from getting a chance of further education then that would be a bad thing; however I'm sure that isn't the case, Essex Uni was glad to have me as a fee-paying student who is likely to be low maintenance, and perhaps to give a slightly wider life experience to the other students.
Well done, Arch's mum, for getting her degree. It was probably for her own personal enjoyment and satisfaction but I don't think there's anything wrong with that, and I think it's easier to appreciate education when you're older and have chosen it, rather than just ending up there by default.