My dog has leaky . she isn't pregnant so why?

Most likely being around the kittens has caused her to lactate poor thing. If she's having some pain there she could be going into mastitis (because the milk is clogging). I suggest you keep her away from the kittens if you can, see your vet for help in tering this milk (if there is pain, this needs to be done) and maybe it's time to have her spayed because this is likely to happen again, after her seasons. And don't try to express any milk because this will only encourage her to make more. Also cut back on her protein/food but make sure she's drinking.