Clearly it is. She is bringing a lot of attention to the problem of anthropogenic climate change. If she weren't, you wouldn't be repeatedly asking questions about her and trying to disparage her.
Let's say I offered you a deal, where if you give me a hundred dollars, I gave you a million. If you believed that I would actually deliver, you would jump at the deal. Why not? It would be a smart investment. A similar argument can be made for Thuberg's carbon footprint (or Al Gore's, etc.). The actual CO2 that comes from a single person's actions is relatively small, but their actions may make a BIG difference limiting future emissions.
This really is not that hard a concept to understand.