Ask her to stay and play.

"Wait," you say, "Don't go so soon, Rachel."

She stops and looks back at you, curiosity filling her eyes.

"By my count, I've got about six holes that I can fill. I doubt I can do that by myself in fifteen minutes. But..."

"You want me to stay and help you fuck these sluts, right?"

"That's the general idea," you reply, not stopping your face-fucking of Pippa.

"...hmm...okay," the brunette says, "It sounds like fun. Switch over to Dharma's face for a while while I get the two things that we'll need."

You nod and pull out of Pippa, who pants for breath now that her mouth is free. You hear Dharma whine and beg for mercy as you slide the handcuffed duo over a bit on the bed, putting her in position.

You line up your dick with her lips, showing her no such mercy. You pinch her nose until she opens her mouth, putting an end to that defense.

After a couple minutes of face-fucking Dharma, Rachel returns, pushing a metal cart into the room.

When she moves out from behind it, you can see that she's sporting a massive strap-on. It's a bit shorter than your actual dick, but it's thickness makes up for it.

She walks around the side of the bed and whispers some instructions in your ear. You nod and agree to follow suit.

The two of you lift up the naked and handcuffed duo of Dharma and Pippa & slide them onto the cart. Once they're on it, you two slide the cart back around to the front of the bed. They struggle valiantly, but this lessens when they realize that they might fall off if they do it too much.

Without warning, Rachel shoves her plastic phallus down Pippa's throat, face-fucking her in the same way that you did.

"She'll have me lubed up in a minute," Rachel says with a smile, "While she does that, you decide who you want to fuck first."