The female dogs in heat usually have fluid discharge from their private parts. But if you think that your dog is not in heat, then there could be any problem with her reproductive organs or urinary tract. You should take her to a vet in this case.
My Dog Has White Stuff Coming Out Her Vagina What Does That Mean?
Its a yeats infection I would go see your local vet
My mums dog had this problem and was told by the vet that the dog had a chill in its privates and that it would go away on its own also can happen around a seison
Well, is it blood? If so its her period, if not blood what color, etc? Dogs can have a slight discharge the same as women do, but if its foul or a lot then I would see a vet.