In reply to Blue Straggler:
> but made it quite clear from her reactions on meeting him again that she still loves him .
> No she didn't. This was pretty much the best bit of a film that I otherwise didn't particularly engage with. A smart bit of nuanced acting, great editing and some cinematic sleight of hand. She was merely having a little moment of recall, a lightning-fast "what-if" (the whole montage) and a return to her reality which was hardly a harsh reality.
What I also liked about this bit was that the flashback was typical Hollywood fantasy, fake sets, costumes, soft focus lens etc. - in contrast with the rest of the film on real sets, with real clothes, with no fakery*
As you said, it was a surprise ending, in that she had the flashback, we all thought they would get back together, but they just winked at each other, saying "... Nah. - but thanks"
* except for the weird flying bit in the planetarium, which I still don't get, unless its a reference to the fact that it was the set of the film they were watching.