This one is tricky, but possible. Start by thanking her for all her help and advice. Then, tell how important it is for you to test your new-mom wings, and remind her that the best way to learn is by doing it yourself. After all, isn't that what she did when you were born?
You can also try to push Mom back without pushing her away by attributing your information on baby care to a professional. Next time Mom says, “well, when I was raising you…” Respond with, “oh, I talked to the doctor about that and she said…” One last thing to keep in mind: New moms really do need help. Set some boundaries... but don’t close the border.