Why does she have milk? Is she nursing a litter? Did she have a false pregnancy? Out of the blue start producing milk?
If she has her own litter, depending on how big it is, she might could foster a puppy or three.
If it's because of a false pregnancy, then it's a qualified maybe. She might not produce enough, or good quality enough to foster a puppy.
If it's out of the blue, I'd want to track down the reason why she's suddenly got milk.