I would ask her parents to get an idea of what she likes/wants. What are her hobbies, is she into sports at school, etc.
Sweet 16 is a huge bday. My daughter will be 16 in late December.
If she is getting a car, I might get something car related for her.
My daughter loves cash/gift cards. She buys her olwn clothes and accessories. She has one of the new IPhones and she loves to switch out the protective cover on occasion.
What type of things does she like? My daughter has a really nice bracelet and necklace byt Juicy Couture. LOVES them as well as some of the Juicy and Coach bags.
If I didn't know which route to take, I would be extra generous with cash or one of the Visa gift cards she can use anywhere.