I'm working on a campaign (DnD, 5e-based, Forgotten Realms with some customizations) in which my party would go through a land in which one of my players is not welcome, because of her race. She's an elf, and humans there don't like elves: some fear them, but some sincerely hate them, to the point they may even harm them.
However, I have customized my Elf races to appear more human.
I know I may face criticism about featuring racism or other forms of discriminations, but it's actually part of the plot and it's important that it's there. Plus, I'm not convinced that the fantasy world should be an idealised version of our culture. But let's get back to the technical question.
A character in the party is an elf, but she clearly has to stay with the party (unless they explore different options, but let's suppose they don't). Her appearance his sufficiently human-like that she could get away with some make-up or by dressing in a certain way to hide all elf traits.
What are the different levels of "elf detection"? For example, common people may just think she's a short, thin girl, but an "elf hunter" could notice certain behaviours, or a special attitude (which ones?). Is there magic that can detect a person's race, and if so, can it be fooled?