From what I know about Greta, she is rather careful with such matters. Your comment in general is in effect destroying part of those careful efforts, so I'd be happy if it wouldn't.

"Significant carbon footprint" asks for, significant compared to what? Maybe Greta leaves bigger footprint than the lowest, say, 10% of the Earth population, who don't really have access to modern technologies with that significant footprint. But she surely tries quite a lot given the circumstances where she is, and encourages us to follow. So I'm skeptical about accusations towards her without enough evidence.