Of course she has to want an oval! Joking...
But I am having some serious problems just knowing what measurments, Cut and such will make this a good diamond?
Some stones are hard to buy online.
Consider buying an ideal-scope and going shopping, or send it to the vendor and ask him to go thru his stock with it (if they have physical stock).
You will find information that will help you know when an oval is likely "right"... You must plan on looking at it yourself to be certain it is right for you.