I'd say... Consider a skirt/top combo, too! Aside from that...
Texture or maybe diagonal stripes or a small pattern on the bottom half and block colour on the top half could help with the proportion. A peplum skirt or top, or a full skirt (think: 50s swing dress) could give more volume below the waist. Wide, even super wide belts are good for nipping you in at the waist. You could go for a little shrug or cardigan if you find something awesome but sleeveless. Also handy if it gets cold
A wide scarf could do the same thing.
Just thought of something!! I'll show you my dream dress. Pricey, but when I hit goal I'm saving up for one! This would work really well, I think, or something along these lines. Also, still dressy and unique, but not glitzy or overdoing it
Have a lovely time, and congrats to your daughter on her graduation!