Put your foot down.

"Riley Marie, that's enough." You're done yelling, and more spanking probably won't help, so you settle for firmness and calm. You stand up out of the water, looking down at her. "This behavior ends right now. If I have to tell you again, then your mother is going to hear about it, and then we're all going to have a nice chat with Gina." Gina is your family therapist. You haven't needed to have a session with her for some time, not since Riley was 16, but the threat seems to do the trick. Riley sulks, but she nods.
"Fine. I don't see what the problem is...but whatever." She flounces back into the water, rubbing her ass and wincing. "No more."
"Promise me."
"I promise, daddy."
She's not happy, but you don't care. You can't let this sort of behavior slide. It'd be too easy to let things...happen...that shouldn't. As it is, you're going to have some really fucked up dreams, you're sure.
"Don't spend too long in there. Big day tomorrow."
"Yes, sir." She was mocking you, now. You give her a level look that wipes the smirk off her face.
"It's not too late to return your birthday present, Riley."
"Sorry...." you think maybe that was the last of it. You head inside, grabbing a beer and draining the whole thing as you climb the steps to your room. Sleep is slow in coming, with your emotions all jumbled between Jenna's vicious streak and Riley's insane behavior. Perhaps in the morning, things will be back to normal.