Moving closer for my girlfriend's hobby sucks.
Why don't you want to be close to your girlfriend's hobby?
The hobby takes a lot of time to train for, which results in me spending less time with her.
You shouldn't have to relocate just to be closer to your gf's hobby like that. She can live there and do it herself.
What if my girlfriend doesn't get it?
Then I guess she wasn't the right person for you. She should understand that asking you to move for a hobby that takes up a lot of your quality time with her is very selfish of her.