I'm not sure if this is normal but I don't think so, But either way it is symptons of pyo so I would go off to the vets just in case. It's not worth the risk when you bitch is involved is it?
Same thing happend to my girl 3 weeks post mating, we took her to the vet and she said it was a slight infection after mating, she was put on a course of anti-biotics and she was fine,!