Her husband has top billing in Sleepless in Seattle, but Rita Wilson, who plays Tom Hanks' hopelessly romantic friend, Suzy, steals the show with a three-minute monologue. As Suzy describes the maudlin plot of the Cary Grant- Deborah Kerr tearjerker, An Affair to Remember (in short: boy-meets-girl, bus-paralyzes- girl, girl-plays-martyr-and-doesn't-tell-boy-what-happened), her voice catches, her breath becomes short, and she slowly dissolves into convulsive sobs. By the end of Wilson's scene, it's impossible to decipher what she's saying, but it doesn't matter-the emotional flood Wilson's character unleashes gets the point across: Even the sappiest movie can be devastating. Both Affair and Sleepless are fairy tales of love at first sight, but the Hanks-Wilson courtship followed a different script. ''It was very When Harry Met Sally...,'' says Wilson, who first met Hanks over a decade ago when she made a guest appearance on his ABC sitcom, Bosom Buddies. ''We had a slow, gradually building friendship, which blossomed into a wonderful relationship.'' But it wasn't until they were cast opposite each other in Volunteers (1985) that romance stepped forward. Two and a half years later, they were married. Though Wilson, who's in her mid-30s, first saw the Sleepless script because her husband was up for the part, it was her crying that won her the small but memorable role. And she couldn't have done a better, wetter job, according to director Nora Ephron. ''The whole crew burst into applause when she was done,'' Ephron says, ''and I knew right there we had a scene people were going to die from.'' How did Wilson work herself into such a three-handkerchief frenzy? She pretended her legs were paralyzed, a la Deborah Kerr in Affair, by holding them stiff under the table and covering them with a dinner napkin as she spoke. ''It helped me feel more pathetic,'' she says. Hanks, true to his uneffusive Sleepless persona, passed on the chance to view Affair alongside his wife. ''I asked Tom to watch it with me,'' says Wilson. ''He looked at me like, 'Yeah, I'll be right in-not.' He came in at the end when I was wiping my eyes. I tried to be pretty objective about the movie, but it's manipulative. I cried, yeah. Anyway, I wasn't sobbing profusely.''