Hi Gina, if your
Bibbidi Bobbidi Boutique reservations are at the Downtown Disney location (in the World of Disney Store), you are all set. They actually have a Hannah Montana package available there. It includes: Hannah Montana (HM) sequined wig, HM face gems, HM costume including tutu, microphone, HM "backstage pass", make-up kit, photo shoot and photo for $153.15.
Another option that both the Cinderella Castle and Downtown Disney locations offer is the "Pop Princess" hairstyle. This includes a colorful hair piece.
If your little girl has her heart set on Hannah Montana, then you'll definitely want to make reservations at the Downtown Disney location. Be sure to book it early enough to allow plenty of travel time between there and the Magic Kingdom for your Cinderella's Royal Table reservations.
Hope this helps and please let me know if I can assist you further.
Congratulations on adopting your little Princess,
Kaylene