Why would a two month old baby get scabby skin on her head?

It's most likely "cradle cap" which is dried skin layered on top of itself. If you got one of those really soft plastic scrubbie brushes from the hospital then when you give your baby a bath, soap up the scalp and gently scrub off the excess skin. It will probably take a few times and your baby will seem to have "dandruff" for a bit but it will go away if you work at it.

If you didn't get a scrubbie brush, look in the grooming section of the baby department. The idea is to get a little extra power than a wash cloth but don't hurt the baby. :D