I would keep her on that food, since she has other more importnant medical issues that need to be addressed.

A tablespoon or so should be ok for a dog her size. Basically anything that can produce larger stools, which helps push on the glands as she defecates, which helps naturally empty the glands.

It can also be allergy related. Is it worse at certain times of the year?

How old is she? Did anything change when she first started to have these problems?