"Yes," Sam said immediately, unscrewing the cap from his flask. He wanted to throw the water into her face, but he figured that would be considered terribly rude. It wouldn't have been rude if this 'Trish' was actually Ruby, but on the off chance that there wasn't a demon hiding underneath that pretty face, Sam was going to make sure that he approached her with his manners. Even if it was difficult, considering how tense he was already beginning to feel.
"Here." He thrust the flask of holy water at her. "Drink it." A swallow would have proven enough. Smoke would fly out of her mouth, she'd start howling in pain. Otherwise...they'd have a lot of explaining to do. Which would be unfortunate, because Sam would have really preferred to send a demon back to explaining his issues to someone who reminded him of the one demon that seemed to be bothering him the most.