Lee's lakeside and all of the restaurants in that building are now shut down. Hue is a trandy restaurant in the downtown area, but may not be the romantic sit down that you are looking for. Sam Snead's(I used to work there and hate to suggest it, but) also provides a nice menu and on most nights it is not very busy, there is also a back area that is nice and dimly lit or there is a patio for a georgeous view of Lake Eola. And after you are finished you could always take a stroll around the lake. Average entree costs a little over $20.
For a restaurant that she is going to love, but may cost you a little over $100 including tip, but not including alcohol, is Manuels on the 28th. This restaurant is on the 28th floor of the Bank of America building in Downtown Orlando and provides a great view. I would definitely call ahead for a reservation and ask for a window seat, I don't know if they have anything else, but just make sure. Once again, a little pricey, but she will absolutely love it.
Just remember, alcohol is very expensive in these places, so if you are old enough to drink and want to impress her a bit order a not too expensive bottle of wine $20-$30(make sure you take the menu and order/act like you know what you are doing). This $30 bottle will give you about four drinks, almost the same as alcohol, but will also give the impression that you know what you are doing. Plus, ladies love wine, oh yeah, don't forget to ask her what kind she would prefer, you don't want to be too overzealous.
Sorry for the dating advice and good luck