Hi Jolene
Believe it or not this is a relatively common problem and is often associated with marking for what ever reason. This may be to increase her familiarity with your nice clean smelling duvet (anxiety issues) or she might have some status issues. Without seeing the dog and your relationship with her it would be difficult for me to give you any advice as all problems are individual. However, a good qualified behaviourist should be able to help you and I would suggest that you ask your vet to recommend one.
For now clean your duvets and do not allow her up onto the beds. It would also be sensible to have her checked by your vet for any medical conditions related to urination.
Sorry not to be any more help but behavioural problems are usually complicated and need one to one help.
Rosie Barclay