If she's had a good relationship with her pediatrician for many years, and feels comfortable talking with him, then a change may not be necessary. A change could make asking questions more difficult if your daughter is shy or takes a while to get comfortable with a new person. You also need to consider the abilities, style, and comfort level of your current pediatrician. Many pediatricians are trained to take care of adolescents completely, but there are also a number who are not.
A physician who treats adolescents needs to be able to provide time and opportunity for the teenager to ask questions and participate in their own health care management. The physician should be able to manage common adolescent issues and provide education on topics such as: breast self exam, gynecologic issues, risk-taking behaviors, and nutrition.
Some male pediatricians have a female nurse practitioner in the practice, to help provide these services. I think it would be reasonable to talk with your daughter first to see how she feels about her current pediatrician. It is also perfectly reasonable to ask your pediatrician what he thinks, and if he is able to provide comprehensive adolescent care. If the answer is no, then your pediatrician may be able to recommend another provider for your daughter.