Hi Deanna,
It's been awhile since I've been on a Disney cruise, but my understanding is that there is a character breakfast on the 7-night cruises only. If you are traveling a shorter time, you may want to verify that information. I just wouldn't want you or your daughter to be disappointed.
Snow White can be found daily in the Germany Pavilion in Epcot. There is a sign with times when she can be found, so getting a picture or photo with her is fairly easy, and having your little one dressed up as a miniature version of her favorite princess would make an adorable photo.
If you want to splurge. Make an appointment at
Bibbidi Bobbidi Boutique. Your little one can get a princess makeover. Afterwards, let her put on the dress and enjoy her day in the Magic Kingdom.
No matter which park you go to, you're sure to see dozens of little girls dressed up as their favorite princess.
Hope this helps. Have a magical vacation!