Frisk half-expected Sans to reject her promise. If he did, she wouldn't blame him. She wouldn't take her word, either. She anxiously waited for his response, and when he relaxed so did Frisk. That was a good sign, right?

She returned his tight hug, waiting to hear him speak. Upon hearing his thank you, she simply smiled and held him a little closer. She didn't want to move, either. Then again, she never wanted to move away whenever she hugged Sans. He had a powerful, calming effect on her. Even now, when he was so broken, she found comfort in being in his arms. 

When they finally broke away, Frisk watched as Sans stood. She remained on her knees for a moment, taking in the sight of the brothers standing together. She was just about to get up on her own, when Papyrus held out his hand for her. 

Frisk let him pull her up, and once she was on her feet she put a hand on Sans' shoulder. "Yeah, hot chocolate fixes everything." She softly laughed, then turned to make her way back down the stairs.

Back in the kitchen, Frisk grabbed a paper towel and wiped up the small spill on the table. She cleaned off the drips from the sides of her mug, then tossed the paper towel and sat back down.