Good Luck with your puppy, although she really is too young
It sounds like you did get her from a puppy mill which would also be why the breeder was willing to let her go so early.
You have a lot of work ahead of you to help keep your puppy healthy this young. You are basically going to have to take place of her mother for a while. Here are some things you need to do.
* You need to feed her every few hours and make sure that she eats. The best way to avoid hypoglycemia is to make sure she eats well and eats often. If she isn't eating well, which is very likely, then come back on here and we can help you out. I cannot stress how important it is that she eats. If you don't know about hypoglycemia then you need to research it because you can lose your puppy to it quickly.
* Get some nutri-cal or something similar and carry it with you at all times.
* You also want to avoid leaving her alone for any length of time.
* You are also going to need to keep her warm. Puppies this young sometimes have trouble maintaining their own body temp.
* Since she has missed out on learning socialization skills, she is going to have some behavioral issues in a few weeks like domination, biting, and barking. Puppies who are taken away from the mother this young are difficult to train. Get a good book on how to train because you are going to have to teach her the skills that she normally would have learned from her mother and littermates.
I know that the others on here can think of a few more things to help you out.