Have celebrated a few teen birthdays in the world.
Does she like any particular type of cuisine, or is she interested in any particular country? You could have dinner in the world showcase at her country of interest.
Is there a tour she might like, double checking ages of course. Many of them start at 16.
Special birthday package from Disney florist?
Here's one you can modify from a Christmas gift for a teen. Went to each country in the WS and chose something under (pick a price) and filled the stocking. You could do a birthday gift bag...
If you want more of a night life experience (no idea how mature she is or what sort of expectations you have) you could take her to City Walk. It's not Disney, but it does have night life!