Just wanted to note: If the mum isn't around, you can stimulate bowel movements and urination. Take washcloth and warm it with some tap water (not hot, just warm). Put it around your finger and stimulate the anus/vulva to simulate a mothers licking. This generally works with most of the orphan kitties we get at the clinic.
Although you did say she was defecating and urinating elsewhere, I too am curious about the real age. There's no use trying to get her to use a litter pan if she really is that young. Keeping up with lots of fresh towels/newspaper in her area may be all you can do until she is a little older.