I really like the beach too! And the sun, which is mainly absent here!! It is crazy, I rarely go to Hyde Park but don't live that far from it, but that is always the way. I never went to the monuments in DC either... I should make more of an effort.
She will have a great time seeing the world, don't worry too much, she'll be quite alright. Europe is surprisingly "super-safe" compared to the US. That is a nice, long trip for her. She won't be rushed and will have lots of time to enjoy the experience.
I'm taking it one day/appointment at a time. I think I'd regret cancelling the cycle if it weren't advised, and it went worse the next time. If at any point they suggest or hint at cancellation, I think I'd certainly go that route. I am trying to stick to the quality over quantity mentality, but it's all as you say 'easier said than done'.