That's right, it's fishy kinda smell... more like rotten fish
Our yorkie has this allergy to something on the regular food, which caused dry skins thus very itchy for her & she scratched a lot.
Our vet recommended the Hills Prescription Diet Z/D, she never had the dry skin anymore, but it's quite expensive. Our vet told us to use this Z/D for like a year and then start trying other brand.
So we did, we tried Eukonuba, Natural Choice, Science Diet, and finally we found the Royal Canin works ok.
Why do you say Royal Canin is not good?
Back to anal gland "leak", what can/will the vet do? will she need operation or somesort? she does not do it often, just a couple of times a week perhaps, and more likely to do this during car ride or when we watch movies (weird) perhaps she can't stand the noise.