The person seems not only underdressed for the occasion but also bewildered and alarmed! You could mistake the way she immediately falls over for a dramatic dance move if you were very generous.

The crowd is apparently feeling pretty generous!

(The singing that's happening is in... Spanish?  The performers all have (conspicuous, bedazzled) earpieces and the speakers aren't optimizing for sound quality as heard from the stage itself; it's nearly impossible to make out any words despite the volume.)

Once she's done belting out the last few lines of the chorus, the lead singer walks boppily over to apearee and offers her a hand up with theatrical enthusiasm.

"...gracias?" murmurs Bella, standing up.

The verbal component of that gets absolutely no response!  But the singer telegraphs very clearly that Bella should allow herself to be led across the stage and then continue off it, where there are quite a lot of people in T-shirts and lanyards observing the action.  She gets blown an exaggerated kiss before the singer turns back to center stage to soak up her applause.

The T-shirted lanyarded people are quick to usher her further into the wings and sit her down on a folding chair.  The lanyard closest to her apparently belongs to one Mercedes Garza, working at the Gira de las Mariposas de Arillegua Ortega 2033 as SEGURIDAD.

That's so valid of everybody involved. She will sit on the folding chair and catch her breath.

The audience calls for an encore and Arillegua obliges with only a little play-acted reticence.  A different security person hands Bella a bottle of water.  The staff are talking to each other but it's still loud enough that she can't make much out; they seem to be relying on a network of (rhinestoneless) headsets to understand each other.

It's hard to go far wrong with drinking a bottle of water. She will go ahead and do that though thirst is not actually primary among her issues with the situation right now.

When she's gotten a ways through it, someone hands Mercedes a headset, who fiddles with both that unit and her own before placing the spare over Bella's ears.  The sound cancelling is pretty impressive; she can barely hear the performance with them on.

"Are you alright?" Mercedes asks her, in Spanish.

"I am very -" What is Spanish for 'confused'. It's going to be something obviously cognate but she doesn't know what specific cognate it is. "I do not know what is around me or why I am here."

"Heard."  She nods sympathetically.  "Did you take any drugs tonight?"

"No, but I would not believe me to say this."

"Did you hurt your head?"

"My head does not hurt. Maybe though."

"What's your name?"

"Bella. - Isabella Marie Swan. American."

Mercedes slides a strange electronic device with a weird screen and a weirder keyboard out of a pocket on the side of her thigh.  She holds it with her left hand and presses buttons with her right (the object being shaped such that this seems about the only practical way one could interact with it).  'Isabella Marie Suan American, "Bella"' appears on the screen.

"Okay, Bella, and what's the date today?"

That's a wacky doodad, is it like a specialized Blackberry or something - "Uh, it was Tuesday, January 25, 2005. But I'm very not know what is around me."

She can see a bit of a stylized butterfly logo peeking out between Mercedes's fingers though not whether it incorporates the Blackberry one further down.  "...Do you normally take any medications?"

"No."

"Did you come here with anyone, that you know of?"

"No."

"What do you remember from before we started talking?"

"I started being in the -" she doesn't know stage "music floor. Before that, I was in a cold place of cars. A car on the - cold water - ice! a car on the ice - came toward me."

"...Okay."  Mercedes starts navigating to something on her gadget, which apparently also has a little ThinkPad-esque nubbin on it.  "Bella, I know basic medicine and I'd like to check if you're okay in some ways that involve touching you.  Would that be okay?"

"Yes." Sigh.