

I think this has something to do with the relations between Swann and the narrator, Marcel, as well as with Proust's own homosexuality.

In fact, he begins hounding her with questions about her attraction to women, and she lets slip a sort-of admission - but why does this point disturb Swann so much? Why does he keep picking at this particular wound to his ego? In some ways, you'd think he would be indifferent to her relations with women - the real threat to his ego would be if she threw him over for other men (he of course has no sense of remorse about his own ongoing relations with other women while he was pursuing Odette).

Not only does Swann become obsessively and irrationally jealous about and suspicious of Odette, in Proust's "Swann's Way," but toward the end of the Swann in Love part, a novel unto itself, he becomes tormented by the idea that Odette is bisexual, or at the least that she has had several affairs or relationships with women.
