Hi Maha,
Congratulations on your graduation from medical school! Coming to Walt Disney World to celebrate with your best friends sounds fabulous. Let me offer you some thoughts on where I like to have celebratory meals at Walt Disney World.
California Grill is a special restaurant. From high atop Disney's Contemporary Resort, you can see the nighttime fireworks at Magic Kingdom. The feeling at this restaurant is fairly upscale, and the food is delicious. Be sure to try some sushi!
Another dining experience that I really enjoy is
Jiko - The Cooking Place at Disney's Animal Kingdom Lodge. Here, you can sample African cuisine and choose from an extensive African wine list. The decor is beautiful, and after dinner you can head out to catch a glimpse of animals such as giraffes on the savanna.
For options inside of a theme park, I think that some of Walt Disney World's best restaurants are in Epcot's World Showcase. I celebrated my birthday a few years ago at
Chefs de France. This is a bustling bistro atmosphere, and while more casual than the options I listed above, still provided a fun backdrop for my celebration.
Finally, consider
character dining. It sounds like you will be traveling with a group of adults; however, character dining is fun for all ages. I am sure that the characters will celebrate with you if you let them know that you are celebrating your graduation!
I would love to help you plan more Maha; however, I am limited in the space that I have to answer. Please do write back if you have any further questions.