Did Arwen know?

[Lobelia]

The Luthien-Beren comparison was pretty obviously deliberate on Tolkien's part. Love at first sight does seem common in his fiction, though an aristocratic thing - Sam and Rosie are peasants and have known each other for years; I got the impression Rosie was his girlfriend, perhaps even his fiancee, who pointed out that he'd had his fun and she'd waited over a year and it was time to get married, thanks. They are not the stuff of mediaeval romance, or meant to be. Faramir did seem to fall in love with Eowyn pretty quickly and let's face it, they were engaged after about a week! :-) Maybe one of those things you do when the world is coming to an end and there's this really nice person of the opposite sex in the next ward...

As for Aragorn, he was a romantic-minded boy when he met Arwen, day-dreaming about their mutual ancestress and suddenly, there she is, the woman of his dreams, in the flesh! Maybe Arwen had similar feelings, after all those people saying, "Did anyone ever tell you that you look just like your great-great grandmother, dear?" (g) and she felt that if she looked like Luthien she would probably fall in love with a mortal and lo, here was this good-looking mortal boy, obviously smitten, just like Beren...