Being a leader of a 9 members group isn't easy. It must've been really difficult for her to control all the members. Consider all the responsibility she had to take. She had wanting to step down from being a leader before, but I'm glad she didn't do so. The other members wouldn't have fit this role.
There are many words I would use to describe how special she is, like charming, talented, beautiful, dorky, funny, and more. Again Happy 25th Birthday Taeyeon ^.^!! Have a very succesful career Taengoo, Best of luck in the future, and stay dorky.