It's the adults behind her that have got under the skin of people to be fair, nobody could be angry with her she's just a pawn in a bigger game. Carbon offsetting is a way that you can still use carbon high activities but pay for research into greener options, which IMO means that rich people can offset their carbon footprint and continue to pollute.
We have to seriously do something drastic to limit our plastic use and the way we go forward, but this carbon offsetting is similar to me going round punching people in the face but giving money to a shelter for abused people, so the next day I can go round punching people in the face because it's OK I have offset it.