Burddom, one more thought that may or may not be of use: it sounds, from the description, as if by trying to accomodate her needs you are in fact rewarding bad behaviour. Maybe you could consider to allow her to beg for it, rather than to nag, instructing her in exactly when and under what conditions that is allowed.

Failing to comply with your conditions would be an automatic No, following instructions would be a maybe - if she succeds in arousing your interest.