It's two films in one:
1) It's a slice of life film about a young woman who has her sexual awakening when she falls in love with another woman, each playing a different role in the relationship, each having a different sense of her own identity, and each coming from a different cultural background
2) It's a film about how people change and grow apart, and the consequences of how personality traits and backgrounds shape your outlook as you mature, about how love is not enough, and about how devastating loss can be.
But it's mostly driven by the characterization--not only of the girls, but the world they inhabit (the fight in the schoolyard, the two dinner scenes, the scene at the political march/demonstration, and the scene of Adele hosting the artists provide good background of this), rather than plot.
It is definitely not a lesbian film (I'm not even slightly convinced that Adele is a lesbian). I think the films cultural politics are probably more fleshed out than the politics of sexual identity described in the film.
