By five weeks, she may be already weaned off of the milk and able to eat puppy food or puppy mush. Some breeders have them completely weaned off of milk by 6 weeks even though they still keep the pups longer. It sounds like the mother dog could have eclampsia (sp?). This is a calcium defiency and by letting the pups to continue to nurse off the mom could cause the mom to die, her body can't handle it. Actually there is a thread on someone who is going through this. Here is the thread...
http://www.yorkietalk.com/forums/showthread.php?t=56197
I would have some nutrical handy and make sure the puppy is eating plenty and limit her playtime or exercise. Also make sure the puppy stays warm and does not get chilled. Good luck with your puppy, she sounds cute!!!