50th Anniversary Italian?
Spiaggia is the tops in the city. Its on Michigan Ave. FYI, its very upscale and formal (Jacket required) and pricey (tasting menu for two with wine pairings is around $650 for two. They also have a la carte if you prefer), but after 50 years, she deserves it, right? That's barely $10 a year. Reservations are a must.
If that's not your style, they also have a Cafe Spiaggia next door which is less formal with a more limited menu (but same kitchen.) Or Coco Pazzo is a very nice place within a 5 minute cab ride.