I'm surprised by how many people here are making this about the messenger, rather than about the message. Typically we strive to ensure the former is not the focus.
Discussing the hype that is surrounding her makes for interesting conversation. Discussing whether her delivery seems rehearsed, or her credibility due to her youth, is missing the point by a mile.
The problem is not that she is 15, or of voting age, or a girl, or being used, or being made the face of a movement.
The problem is that people have such a hard time focusing on the message rather than the messenger.
If she is right, we should be behind her. If she is not, then we shouldn't.