Hi Tamula,
Welcome to the Moms Panel! It is not at all uncommon for children to get nervous around the characters, and my children have always been more comfortable with the face-characters such as the Princesses.
Since the characters are a very popular feature of a Disney Park visit, typically any interaction with them is initiated by the guest. It is very rare to stumble upon a character without warning! Most of the time you'll notice the long line of people waiting for an autograph before you ever see the character.
There are some great opportunities for dining experiences with the Princesses, my favorite is the
Princess Storybook Dining in Epcot. You can get up close and personal with some of the favorite Disney Princesses, they will sign autographs and take photos with you and/or your children.
Since your child is a bit timid of the characters, I would suggest maybe taking in one of the many fantastic parades. This will give your child the opportunity to see the characters from a distance, and this may build her comfort level with them.
I hope this helps, have a wonderful vacation!