I always tend to come across as a bit of a stuck record on this but I will always maintain nothing beats ballet for coordination and it is incredible for speed too.
I started it years ago to back up my climbing, after some pressure from older and better climbers. It makes you so incredibly aware of yourself that virtually every other activity is made easier.
To give some idea my record at tennis was useless across the board at school, couldn't serve, return or often hit the ball. I didn't play it from that time until I was around your age, around 6 years, when someone in the house I lived in wanted to play and I was the only option. So useless with 6 years to forget everything against someone, who wasn't great but played regularly for fun. I won by some way and found adapting my coordination to the game very easy.
If the idea of tights and plié scares you, go for Pilates or similar. Pilates was designed to back up dance.
Happy birthday by the way and welcome.
