I would have her spayed ASAP, as she could actually be going into heat again very soon. It shouldn't interfere with milk production even if she is still nursing the puppies. Kudos to you for helping this girl and her babies!! Do you know what breed she and her puppies are...or do you have pics?
The mother has some Jack Russell in her and I think the father of the puppies are Australian shepherd??? Not quite sure. Yes, I have some pictures, but I'm new to this site and do not see where I can attach them.