There are two books at the heart of this movie. The first is The Green Ray, by Jules Verne, which is not about a French woman casting about for the right summer vacation. The second is Dostoevsky's The Idiot, which shares that characteristic. But Dostoevsky's Myshkin is seen as an idiot despite being intelligent and empathic, and in the Verne novel, Oliver and Helena sacrifice their quest to see the green ray in favor of seeing each other clearly.

Draw the Venn diagram of those two books, and there's the movie. Like Myshkin, Delphine has her thought out convictions and a sharp wit, even if nobody ever notices it:

“Must make eating with others difficult.”
“Like right now.”

She stands in contrast to everyone who tells her that she should settle for simulacra. One man asserts that the Seine is as good as the sea. Everyone's constantly explaining what's good for her. In Biarritz, it takes Léna all of five seconds to explain how Delphine is screwing up her tan.

Her independence in no way prevents her lonely sadness, but that's the point of the movie. To dislike her would be to think there's something wrong with trying, something wrong with being picky, as she lays out quite clearly in the final scenes. I like that the ending is ambiguous as well. Is Jacques the guy? Is she even going to accept his invitation? She's reversed Verne's protagonists and pushed aside romance for the sake of the green ray.

And boy, that echoes the risks Rohmer took. He wasn't willing to accept a simulation either. He spent months trying to capture the green ray on film before finally getting lucky... or, come to think of it, before finally earning the rewards of persistence.