I didn't really want my girlfriend to enter the race, so I hid her new running shoes
What is the reason you don't want your girlfriend to be in the race?
She is taking time away from me
You are being very controlling by hiding your partner's running shoes. Your partner has the right to do things separately from you, it is healthy to have separate interests.
I don't think it's healthy for her to do.
I think you need to let your girlfriend have her own set of hobbys. You don't have to be together 24/7.