It works, on herself

Sandra celebrated immediately. "Oh!—You did it! I-It worked! You're really getting better at magic, Fiora!"

Fiora, in response, stood there and did nothing. She didn't want to, but her autonomy was out of the question for now. She put herself under Hold Person! Trapped inside her own head, she tore herself a new one.

"That's pretty good, yeah? I-I know you said it was a simple spell, but... ah, it's just so great to see you get it right! Oh, now you gotta do me!"

Fiora's mind fumed. This was supposed to hold you in the first place! Not me!!... Ugh...

"Uh... Fiora?" Sandra started to get the memo, waving her hand in front of Fiora's face, "You can... you can undo it now. Come on, it's my turn! You gotta keep going!"

Fiora silently begged for Sandra to just figure it out already.

"Y-You just casted a spell really well, you got this! Just do exactly what you did, move your—" She stopped.

Oh, thank the heavens!

But Sandra laughed it off. This was harmless. "Well, I'll just, uh, wait for you to come out of it then... whenever that'll be—oh, how long does it go for?"

She looked at Fiora like she could answer. Of course, she did know the answer—an hour or two at most—but that part didn't matter so much.

"...You know, spells can go on pretty long. Maybe I should, like, see if there's a potion around here that'll do the job, yeah? You know, save us some time..."

Not waiting for Fiora this time, Sandra started on her search. Fiora watched helplessly.