Go to a small town jeweler (not mall) and buy loose gems. Look into them and get exactly what you want. I.e., look carefully at diamonds and don't buy anything yellow. These small shops don't own the gems, they get them on consignment. So, if you don't see exactly what you want, tell them to get some more. They gladly will. I've done this many times.
Why loose gems? Give the gems to your wife and tell her to work with the jeweler to create the perfect setting for it. My wife is very particular about the setting for rings, earrings, necklace, etc. I find that it's best to just buy great gems then let her work with the jeweler.
Suggestion tanzanite. Get 2 largish long ones, marquis cut. Look for stones with some purple in them, not just the deep blue. Believe me, they make gorgeos earrings. Let her choose the setting for the earrings, preferably a low-hanging gold setting.