If you wanna go for the <b>KABOOM!</b> get her Alexandrite.
Diamonds are so common. I don't understand why they are considered so valuble. However, since you're looking for a diamond, SI1's can be trouble especially in the sunlight and other bright lights. I had one jeweler tell me that there were no inclusions.. "umm what are these spots then?" Stuttering doesn't really help a sales pitch.. anyway, be smart and take time looking at various places and always always lowball the jeweler if you're looking at diamonds. Good luck.