When did Alice and Stanley fall in love?

One minute Alice is talking to the seemingly gay Stanley (Hume Cronyn) about her fear of returning to London because she knows she will shack up with the married man with whom she had an earlier affair. The next minute Stanley is undoing Alice's barrette like a pesky brother would do to his sister TO WHICH ALICE ACTUALLY SAYS, "STANLEY, WHY DO YOU KEEP DOING THAT?!" Then when they're about to go down, Stanley hypothetically proposes marriage and she hypothetically accepts. When it's clear they're going to be rescued by the American ship, there's no scene recanting the proposal. Are we to assume this mismatched couple got married just because they slept next to each other for a week or so and had a couple of conversations? I thought it was a very weak attempt on Hitchcock's part. The 'opposites attract' relationship between Kovac and Porter was far more convincing. And it was so because HItch didn't make these characters get all lovey dovey. The most those two would do would f|_|ck - Hodiak knew it; Bankhead knew it; it was a very honest relationship. Hume Cronyn didn't even come off as heterosexual let alone a foreseeable mate for Alice, the nurse.