Hi Nicky,
Hamsters are prone to a condition called 'wet tail' which is quite serious, but located around the tail base and requires urgent veterinary attention. In your case, it does sound like something entirely different, but would still be worth bringing her to a vet for a check-up as it could indicate a skin condition that requires treatment. It may also be a result of self-trauma due to stress (changed conditions etc) or parasites or a husbandry issue such as her bedding etc. Either way, your vet will be the best person to help as they can take a first hand look at her.
Best of luck,
Zara The Vet
[
www.vetvoice.co.uk]
[
www.zarathevet.com]