Follow-up.
So I was able to purchase a pair of diamond stud earrings and she was very happy! Ironically just the day before she was lamenting that she doesn't have any such earrings and wanted to go out shopping for them! I had to make up some reasons as to why that would not work, and thankfully I was able to stall her.
The ones I got her are round brilliant cut, each 0.5 ct weight, SI 1/2 & G/H (around those specifications) mounted on a 3-prong, 14K white gold mount with a screw-on back.
I opted for the 3-prong after looking at a bunch of them because they hide less of the jewel and are more "invisible" than the 4-prong ones.
So mounted they would look something like this:
(Sadly, not to scale! I didn't know how to resize the linked image)
Thanks very much to everyone's input!