If she is 18 or older, she will need a valid government-issued photo ID to get through the TSA checkpoint without a major hassle. If she is under 18, she does not need any ID unless she is traveling on an age-restricted youth fare and then the airline (not TSA) will need proof of age to verify that she qualifies for the fare.
If she is under 18 but does have a passport, driver's license or learner's permit, then it can provide some peace of mind to make sure she has that. As noted, it's not required but TSA can get a little weird about following their own rules from time to time.