Ideally the puppy should not leave it’s mother and littermates till at least 8 weeks of age.
Ten to twelve weeks would be ideal.
I am surprised that the pup even knows how to eat.
If she is tolerating her current diet, do not change her food for at least a month.
Do not add any “milk replacement” but I would soften her kibble with water, you can soak it in the fridg overnight to make sure she is getting adequate hydration.
Please find a local vet and schedule her first appointment asap for advice and guidance.
Puppies are very vulnerable to illness and disease. You need to set up a schedule for puppy shots and such. http://veterinarynews.dvm360.com/new-aaha-canine-vaccine-guidelines-importance-being-date
Good info here http://skeptvet.com/Blog/category/nutrition/
