Girls, What should i get for my girlfriend's 17th birthday?

ok so my girlfriend's 17 birthday isnt until July but i want to start thinking about what to get her. She likes cheetahs, sorry loves them is more like it and i call her my princess and she likes being called that. We will be dating 4 months so i dont know what to get or how much money to spend on her. i was thinking a princess crown necklace from Kay jewelers which is $70. I need a girls opinion on what you think of the necklace or any ideas. this is the necklace i want to get her http://www.kay.com/webapp/wcs/stores/servlet/product1%7C10101%7C10001%7C-1%7C132952108%7C15053%7C