When you and your lady head to bed with another, subtly playing favorites is actually a good idea. This is not the time to be doling out equal parts of yourself to both partiesone of these people cuddles you when you're down and listens to you when you dissect your boss's passive aggressive emails. The other does not.

If you want the intimacy you have to remain intact, give her plenty of love while you're getting hot and heavy. Shoot her looks, touch her constantly, and kiss her plenty. She'll feel great knowing that even with another naked woman around, she's still the focus of your thoughts, and you'll feel good when there's no jealous outburst to interrupt your night.