My first suggestion is to leave the halter on. Use either a leather or breakaway[has a leather or velcro part] Especially @ a boarding facility, cross your fingers nobody forgets to close a gate=loose horse/no halter.
Next, the kid likes to play with her. How? By going in the field and squatting [predator stance-horses will run] or playing tag. Then what you have is a taught behavior.
Then, teach her[and bucket feed treats OK] It is easier to come to you or stand still.
How- Approach her as normal[ look past her not at her eye, and not fast or aggressive] If she stands, put your rope around her neck, then halter on. If she moves away, you send her @ trot or faster. Keep her moving for 2 minutes, tell her whoa, then try again. No luck, move her, 4 minutes this time. Contiue this process till caught, so not when you need to be somewhere else and are running late. Never get mean or angery, just make her do the work. The smaller the space the easier for you, but it will work anywhere. Hint, If she's out with others she will try to get to them, use them, herd-you-her. Depending on alot of variables may take once or quite a few times, but it will work. As the others suggested, once caught don't always work her, feed,pet,brush, etc...Horses aren't dumb and will associate being caught with work. She may easily be caught by someone else. Possibly whoever feeds, or @ certain times. Another option is don't bring her in. If I have a horse who isn't @ the gate when I'm ready to bring in, they don't come in. Funny, but the next day they are first @ the gate.
But you need to try to find out the other stuff also.