For a romantic evening, take her to the North End. This is the Italian section of town, where waitresses will tell you that you must eat more or you will blow away in a wind (all with thick appropriate accent). IMHO, Mama Maria's, tho pricey, is the most romantic in the area. The building is charming, the food wonderful, the wine list decent, and the waitstaff appropriately bowing and scraping. Mama Maria's is off the beaten path, so get directions if you make reservations (which are necessary). You can get real espresso or capuccino and sinful desserts anywhere along the main streets of the North End; for excellent pastries (but not much atmosphere) go to Mike's Pastries on Hanover (anyone can point you to it). Good Luck!
Boston, MA