She shared some photos of her sporting her specially made World Series prosthetic hand.
Hailey had a rare birth defect, called Poland Syndrome, that cause her to be born with three missing fingers.
Engineers used a 3-D printer to create a prosthetic hand.
The 7-year-old is a huge baseball fan and has had a dream to throw out the first pitch.
Now, she will on the national stage.
She's had some practice already, having thrown out the first pitch for the Orioles and Washington Nationals.
Her goal is to throw out the first pitch at all 30 major league parks.