Orgasms make her change back into Nina

"I'm able to physically change back into myself for a few minutes once I orgasm!" she beams happily.

"You what!?" James brings out awkwardly.

"Yea, no shit! Watch this!" she says as she grabs a vibrator from a nearby table and shoves it into her Marissa-crotch.

Next she powers it on and sets it to maximum ****. "This should.. Ah... just take a minute or two!" she moans and starts to masturbate freely.
James watches the spectacle in front of him until finally...

"I'm cumming, I'm cumming!". Zapp, and there was a flash of light and Nina stood in front of him in her own body!

"See, this totally works! Albeit I can stay like this only until the orgasmic sensations subside!".

Now James looked awkwardly at her.