Tiffany is a cheerful, sophisticated, employee at a high-end retail store. She's professional and has the kind of proper, friendly, yet still somehow condescending attitude you find from these kinds of stores. Think the scene in Pretty Woman with the store Julia Roberts tried to shop at before she got her makeover. 

She only has a few lines, so it's a very minor role. Her delivery should be similar to what you'd hear in a commercial for women's health. 

There is a part where Tiffany has to scream because Nashi's arm catches on fire in front of her, but that's as extreme as the role will get