"You're going to punish Donna too, right?"

You are a little surprised by her question.
You didn't quite expect her to be so into this herself, let alone when it came to Jenni and Donna being punished.

She must know Donna's deep, dark secrets (having raised her since she was 18) and how this ties into them.
That or she's just a horny, bondage freak.
You're fine either way.

"I have plans for her. Want to watch?"
"As long as I'm tied up a little, yeah," Dee says with a smile.

Later that afternoon, you have Jenni and Dee tied lightly (but firmly) to some chairs behind 2-way glass.

Donna is naked and tied to a board. She is propped up at the right level to service someone.

A man enters and strips down.
Donna looks him over and says nothing.

"You owe me. I was going to have some real fun with that big titted, blond sister of yours."
"I understand. Let me do what she can't now."

He moves in close and presents his cock to her. She begins to pleasure him.

The pair are more interested in watching the Show than one might think.
Dee's eyes have been opened up to her Stepdaughter's kinkier side...and her own.
Jenni, meanwhile, has seen Donna in action on both sides (before you revealed her presence).
She remembers suffering while Donna orgasmed happily, so she has no problem with this.

She pleasures him for several minutes, sometimes with just sucking...other times with him face-fucking her.
She makes no complaints either way.

When he's done with that, he unties her enough to reposition her in the middle of the room.
Water mists throughout the room, lightly soaking the pair as he moves on to the 'main event...'

He's rough with her, but not painfully-so.
He's just very aggressive and doesn't 'make love to her.'

She cums at least 3 times during this.

When he nears completion, he pulls out and makes sure to cum on her ass.

He leaves without a word.

The only thing left to do is for someone to clean up Donna...