So you disagree with her. Fine. You think she is privileged. So do I, so does she, and she could of course just keep her mouth shut and enjoy that privilege, and have a good time. Instead she speaks out about the things she cares about, trying to speak for those who are not as privileged as she is, and that is what you don't like? Apart from the fact that you think she should speak out about the things you care about, in the way you think would be intelligent. Isn't that your responsibility, not hers? She has picked her battles, the ones that matter to her, and as the saying almost goes; no one can fight every battle but everyone can fight one or two, possibly three. (Four shall not be the number, and five is right out. This has of course been known ever sinece the Holy Hand Grenade Crusade of Antioch)
To me it seems that what it boils down to is that she doesn't do what you want her to do, whatever that is, and she does not do it in the way you think she should do it. And since she doesn't, she can be dismissed as annoying and trendy. Also if you can speak out safely, you shouldn't, because others can’t. Got it.
And maybe climate change is "trendy", but in her opinion, and mine, it is also one of the most important issues all of us, but not least young people, face today, and I welcome all who try to do what they can to lessen the impact it will have.
I do not think you and I can reach an agreement, so I will happily let you have the last word, if you want it, and I will go on my merry way, quite pleased that there are young people who continue to try their best to bring about change in this world of ours, which is not exactly looking its best at the moment.