She tries to snatch the coin, but falls for a decoy

In the terror of that moment, Sarah knew she had fucked up.

In the excitement of seeing how far she could push this, in relishing the power that previous wish gave her in her actions, she had forgotten the trump card, and that no matter how weak she might think that Tom might be, there was a limit to how far he could be pushed.

There was no way to talk herself out of this. There was no way to think fast enough to avoid this fate, or to change the actions that led to this moment.

All she could do was snap her hand out, as quickly as she could, trying to take the coin from Tom and hope her newfound youth would be enough of a trump card that there was no way he would be able to protect the coin.

Just as he said, "I wish that..." she managed it. Sarah snatched the coin from his hand, and immediately opened the door, throwing it out into the parking lot. Not the deftest solution, but she was running on instinct.

A rush of victorious joy rushed through her. It would be okay, she'd still protected her last few hours of being this person, and ensured he couldn't prevent her alteration to the woman she would go back to becoming.

At least, that was how she was feeling, until she realized he was continuing to talk as though nothing had happened, a smile spreading on his face. "...my wife's normal personality will not be altered by the actions of the other people or personalities she takes on thanks to wishes, and that she will be capable of feeling shame for those actions."

Looking around, Sarah realized one of his hands was still at the wheel, and it was clenched closed. "No!" she cried, realizing her mistake. That hadn't been the magic coin, it had been a decoy, and she'd fallen for it.

"I wish that the wish made this morning was reversed now, instead of the previously agreed on time."

And that was it.

Sarah shivered as she felt her clothes, her body, everything about herself change back to how it had been before, to who she normally was.

And with that, she felt the growing shame of what she'd done. Fucking a student in a bathroom, going to a hotel to fuck a man she hadn't even liked just for an advantage at a job she wasn't going to keep.

"I'm sorry," Tom told her, looking genuinely heartbroken. "I know...thanks to that wish, you feel awful, but..."

She took a long, slow breath. "It's alright. I don't even want to imagine just what might have happened, if you hadn't thought ahead to what she...what I was going to try doing. I don't want to be okay with hurting you."

They hugged, and then Tom drove them home, where they would fall asleep and face the next day as it came to them.