I would suggest playing into her fantasies. Bringing it up during sex in a seductive way, not saying, "I want you to go down to the bar and find a man to fuck tonight," but saying something like, "I saw you watching the new neighbor work with his shirt off in the yard today. Did he get you hot? I bet he probably wouldn't mind fucking the married wife next door?" Keep it playful and light and see how she reacts. If she gets turned on by a little fantasy play, bring it up a notch until you give her permission to do what she really wants to do. As some of the other respondents mentioned, if you watch porn together, you can find the porn that interests you both and leads her in that direction as well. Good communication is often being attentive to what the other person is saying both verbally and nonverbally. This applies especially to sex. Don't push her farther than she wants to go, but give her permission to express what she really fantasizes about.