"...believes in?"

"Uh. Thinks that they exist," she says, which sounds kind of insane because, uh, obviously everybody here seems to believe in vampires, but she's really almost sure that most people don't. Probably.

" - oh. ...so we take one alive, show everyone, then they know about vampires."

...this really seems like it shouldn't work, but it's kind of hard to explain why, because, you know, there's a sense in which it really ought to work.

"I don't know if people would believe it. Everyone knows what vampires are, they just think they're - stories. Monsters that people made up. So they get upset when people talk about them, like the priest, because they think that it's a joke."

" - maybe vampires use evil magic on priest, make him lie. We free priest from evil magic, he say vampires real, then everyone knows."

" - I don't actually know if people would believe the priest either. There's probably some way to give people in general enough evidence that they do believe it, I just - don't know what it is."

This must sound so ridiculous, if everyone you know believes in vampires. It's really an objectively ridiculous situation, isn't it.

"God would not let the priest lie!"

That's... debatable. "I think a lot of people might think he was confused, or sick. And - some people probably would think that he was lying."

"If the priest lie, God take his holy powers!"

"Maybe? I'm not actually sure if He would. - but, uh, a lot of people also don't believe in those." The main easily verifiable one she's aware of is creating holy water, and the main way of verifying it is using it on vampires, so....

"They don't believe priests have holy powers? Do they believe a sun in the sky? Or do they say, maybe demons only make it look there a sun in the sky."

"I think people mostly agree on the sun." Man, she wishes that she felt like miraculous interventions were as obvious as the sun in the sky. She's definitely met people who felt like that, but even with vampires wandering around and crosses repelling them, it still doesn't feel quite the same. "I don't really know how it happened. I - guess I have the impression that everyone used to believe, and then in the last couple centuries, people stopped. I'm not really sure how or why, though. ...I did not personally know that vampires were real until I moved to Sunnydale, but like I said, there are a lot of vampires in Sunnydale."

"The work of devils. To make people not know of God. And not believe about Heaven Hell right, that why devils want do that." She is actually considerably more upset about this than she was when complaining her friends were being eaten by vampires. "I need more English, or they not listen when I tell them - vampire -" because she hasn't actually stopped concentrating on Detect Evil. This one came in around the other side, and bothered to disguise itself, since these people were apparently surprisingly prepared to fight. Iomedae runs at him pointing her sword. "Vampire!"

"Hey, kid, I'm just here to return a lost wallet I found -"

She can't smite anymore but she can stab. Even if he were a human and she's sure he's not, a human powerful enough to have an Evil aura like a powerful undead would barely notice the being stabbed. 

Karen is no less prepared for this one. She can get tired, of course, but slayer powers don't run out. She'll knock him back, mostly automatically confirm that his body doesn't respond to the force like she's pretty sure a human one would, and then pull out her stake and - miss the heart, the first time, that's embarrassing, but she can always pull her stake out and try again, at which point the vampire dusts.

" - wait, how did you know that time?" Half a second later it occurs to her that the migrant workers obviously know each other and that one wasn't one of them, but it seemed like a sensible question when she said it.

"I sensing Evil. Also no one return wallet us but I no stab first if he not Evil."

"Right, that makes sense." ...well, the wallet part makes sense. " - how do you sense evil?"

" - holy warriors can sensing Evil. To help fight it. Not all evils but vampires definitely. And demons. And devils. And - dead things not die, and people if they in service of Evil powers, or great evil their selves."

"Oh. That's... useful. I don't suppose you could tell me how you learned to be a holy warrior."

"God picks holy warriors. You have to be - duty and good - always, so everyone know always that if there is a holy warrior they can be trusting them. And you have to learn fighting, so you - do more with strength God give you. And if you ever do bad, God take it away. - you can still make Heaven, God not take away that, but holy warrior powers, those God take away if you not good holy warrior."

....okay, she's gonna go ahead and not read too much into any of that, given the obvious language barrier in play. She doesn't think it's very possible for someone to never do any bad things, but she has approximately no idea whether that's what Iomedae is saying. It's almost definitely way more complicated than that. Maybe you can't commit any mortal sins. That would make sense, not that Karen thinks that means she could manage it.

"You didn't learn it from anyone else? Did you - learn from someone else how it worked, at least, or did God just - tell you." Man, God never tells her anything. - no, Karen, no getting jealous of the living saint before you who's apparently been granted miraculous gifts for being extremely pious and brave. That'd be some toddler level maturity, there.

“My - I don’t have the word -“ she consults someone with better English - “uncle was a holy warrior. He tell me the rules, the - things God give you, the things you promise. They’re holy orders for it, you go there and learn and give promises. I want a holy order, but my father say, too - not big enough. So I wait. But then God make me a holy warrior. I say to my father I am God’s, I go now even if young. He say of course obey God. So I go. 

God choosing feel like - instead of alone, not alone, never alone. And can see Evil. And can call God down on evil. And others can see if they know how that I have holy power. When stronger, can heal sick like saints. When very strong, can ask angels help. Strongest holy warrior walk into Hell save people.”

Man, Karen is really very confused about the general understanding of the supernatural in modern America. She's going to focus on how bizarre it is that there are people in Mexico going around living lives that echo those of the medieval saints, while a good chunk of other people simultaneously don't believe in God, or in vampires, or in anything supernatural at all, and NOT focus on how she kind of feels less special now. Karen doesn't even want to be the sort of person who goes on to have saint stories written about her, it sounds kind of enormously stressful. This is probably part of why she isn't one, which is probably why she can't detect vampires. 

"...what order did you join?"

“I going to my uncle order but I got lost and God led me here instead. So I have no order and do not know all the holy warrior things. Going ask here priest when enough English but priests here strange. No “believe in” vampires.”