Belated happy birthday! 
It is absolutely gorgeous as a bracelet, however it sounds as if your heart is really set on it being a necklace? I vote to keep it as a bracelet for now and then to get it lengthened by Tiffany. $350 seems quite reasonable to effectively get a new piece out of it and it will look beautiful layered with your other DBTY necklaces, especially the platinum!

It is absolutely gorgeous as a bracelet, however it sounds as if your heart is really set on it being a necklace? I vote to keep it as a bracelet for now and then to get it lengthened by Tiffany. $350 seems quite reasonable to effectively get a new piece out of it and it will look beautiful layered with your other DBTY necklaces, especially the platinum!