G.T.
Carrots and other orange veggies can cause this. I've seen babies with it around their mouths, chin, etc. Skin is always wearing off, so it's probably no biggy. If it bothers you, try washing right away, or even a dab of olive oil on her nose just before eating to prevents direct contact. The nose also gets more sun that the rest of the face, so could be a combo of the two, especially if she is fair.