If your woman is a classic girl...then, by all means, get her the classic cut, the classic setting... You can't go wrong there. But, if she's not into the over the top lavishness and bling of the classics, she may find herself looking at one of these beauties in complete awe.
This little Rose Gold 'gem'?
Pop of color, anyone?
Something from the heart, perhaps?
You're her knight in shining armor?
Beauty is in simplicity...
Insanely lavish and peraly white?
For the more extreme...