Agree to let her use the Ruby on you

With slight hesitation, you take the Ruby off again, then hold it out her her, "Alright, go ahead."

"Sweet!" Erica says, snatching it out of your hand and putting it around her neck. You see the amulet shimmer for a brief moment, then vanish entirely from your sight. You get a sinking feeling in the pit of your stomach as you realize that you have no way to guarantee that Erica will ever actually give it back.

Possibly seeing the nervous look on your face, Erica says, "Relax, I'm not going to completely fuck you up, tempting as it might be right now. I just want to play with this thing for a little bit."

She gives you a devilish smirk as she adds, "...And maybe get you back for what you did to me. Now, how do I get this thing to work? Do I just think hard enough in your direction?"

"Yeah, but you've also got to say what you want to change out loud," you tell her.

Erica raises her brow in confusion, "What? I never heard you dictating my changes."

"It's like the amulet's visibility," you explain, "No one else can hear you when you're telling the Ruby what you want changed."

"So... as long as I do it right, you won't know what I'm changing until it happens," she says.

"Yeah," you confirm with a nod.

"Awesome," she says, "Okay, okay, I'm going to try it now. Ready?"

"As I'll ever be," you tell her.

"Alright, here it goes..." Erica says eagerly. You were both relieved and a little disturbed how quickly she went back to the Erica you knew once you gave her the Ruby. If you can just deal with whatever she threw at you, things might go back to normal between you two. Assuming she doesn't go too crazy with it and-

"Done," Erica says, snapping you out of your thoughts.

"Really?" you ask, "I didn't even see your mouth move."

"Well trust me, I was speaking," Erica says, "Now, how long does it take to work?"

"Shouldn't be more than a few seconds," you say, "What did you do?"

"Oh, you'll see," Erica says with an eager grin. It's at this moment that you feel something start to happen.