The general attitude of TRP is to be honest with plates and let them know that you're not looking for any sort of commitment (just sex). Wouldn't being too honest drive some of your plates away? How about dangling the possibility of a future commitment/relationship right in front of her face? Planting a small seed of hope and creating the illusion that she's slowly out-competing your other plates and gaining your affection and respect. Isn't that the more clever and Machiavellian method to employ in this situation.

There is telling the complete truth and there is lying. I am not here to support lying, just the absence of complete truth - and the potential for her imagination to keep her coming back to you.