Should I get my friend a Tiffany necklace for her sweet sixteen?

Im intending on buying her a $100 necklace from tiffany's and I have $400 but I also have two birthdays comin leavin me with a total of $200. This money is something I've acquired after a long long time of being broke and I also tend to be frugal but she is my best and longest friend I've had. Also I have no doubt she would return the favor and also I've skimped on her past presents. Should I buy it for or get her an juicy necklace?