Twisted (1991)

Upon meeting younger co-worker, David, buxom married Christy fantasizes about pleasuring him in the office. Not knowing this, David - who is engaged to be married - reveals he fantasizes about her. Christy says him acting on it would betray his fiancée, but it doesn't mean Christy can't pleasure him herself in his car. Christy and David then develop phone sex relationship, but she wants to go all the way. Feeling pressured, David asks to bring over a friend. The friend slowly gets over the awkward feeling, and David eventually joins in. Christy later fulfills her secret fantasy by pleasuring David right in the office. Finally, David agrees to spend the night with Christy in a motel.