Regarding Greta's transportation: She would have been called a hypocrite if she'd taken a plane, even if it was an empty seat on a plane already making a flight. Voting with our money is a common way of showing what we support...and what we don't. Paying for the seat, would mean supporting flying. Accepting a free seat would have meant advertising for flying.
...As is, she took a solar powered zero carbon emission yacht. Presumably to show that zero carbon transportation across the world is a legitimate possibility. As for the train use, high speed rails are more energy efficient than planes. It might be slower, and more personally expensive than a plane, but it trades the convenience of fast and cheap for the convenience of using that time in productive as well as relaxive ways.
Regarding Greta taking time off from school: Just because she's not doing formal schooling atm, doesn't mean she's not being educated nor seeking further education. There's such a thing as homeschooling, unschooling, etc. If anything, this trip and process she's going through would be an excellent example of unschooling. Among other things, I'm sure she's learning about politics, public speaking, climate science, alternative transportation, and sociology. I expect that she's getting a far more in depth educational experience about these things than most college students graduate with.
Regarding climate change related policies (personal changes and political changes) being too inconvenient and expensive to put into practice: the fact is that we're facing having to make drastic changes, whether now or later. If we start making changes now, we can improve our technology, our knowledge, etc to prepare ourselves to better survive the coming changes. If we wait until the hell is upon us, the changes we'll face will be harder to survive (short term), harder to manipulate, and harder to recover from (long term survival). Basically, either way, we're facing a future different from our present way of doing things. How different depends on how soon (less different) or how late (significantly more different) we implement changes in how we do things.
Regarding her pleas and guilt-tripping: She's talking to world leaders. I'm guessing this batch is primarily made up of older people who have lived their lives already or have established themselves in a soon-to-be outdated economic/socio-political model. She's talking to policy makers who believe that a finite world with finite resources can provide infinite growth for their wallets. She's talking to the people who don't want to make policy changes, because it would inconvenience themselves or their supporters. She's talking to the people that think that sticking their heads in a hole will make climate change go away or pass over them. The problem is, their decisions ARE affecting the future...HER future, the future of humanity, not just humanity but of Earth. So yes, how dare those in positions of leadership and responsibility be so damned nonchalant about this crisis.
Regarding typing Greta Thunberg: A public speech about a topic is different than the actual processing of the information. She had prepared speech points, assistance in editing and refining the speech points, tips on pacing, tone, etc, as well as time to practice. So typing her based on her climate change speeches is rather pointless, as it's not HER your typing, but the result of all that combination. It would be better to find spontaneous videos of her interacting on topics/activities other than climate change, as those would be closer to the real her.