My son went from 3 to 2 somewhere around 6.5 months. Pay attention to your baby, not the books! I'm sure she's fine, and like you said, she wouldn't be sleeping if she wasn't tired. I believe Wyatt took about a week to readjust his schedule and his bedtime moved WAY earlier (he was going to sleep around 5pm for awhile, and then day light savings didn't help either), but it gradually got later and he now sleeps from 6:30-6:30 and naps from 9-10:30 and 1:30-3 pretty consistently. I didn't do anything to encourage his schedule change, just paid attention to his sleepy signs and tried to stay home more so we weren't out and about when he was getting tired and needed to go down for a nap.
Jennie, mama to Wyatt (3/25/09) and Emma (11/22/10)