I suspect she hadn't fully understood, or to be more precise, they hadn't fully understood, that to a great extent the role of the Royals is a ceremonial one, and doesn't leave any room for political position taking, even ones that seem 'righteous'. Charles might be a little bit to blame here, he is convinced he will be allowed to continue to gob off about stuff once he is King - he won't (or, at least, if he does, that will be the end of the Monarchy), so it isn't surprising that his Son thought he could do the same. So what with them going hard on Green issues, they probably didn't realise that this would be frowned upon and open them up to public scrutiny / criticism. Perhaps they should have spoken to a few MP's before they started, they would have set them straight on how the press would react. She hasn't come across very well, it all seems a bit 'me me me me' with her, but who knows, perhaps that is down to slanted reporting.
The best thing now would be for them to relinquish their royal titles, so that they can't be accused of profiting from them without doing the public duty part that usually comes with it, and try and carve a life out for themselves (probably in North America, but maybe here), whilst not receiving any public money whatsoever.
I wish them luck.