We tried - it's a boy, now 16, I think if it were the daughter, she'd do it. Kid told mom two years ago we had eye and doctor's appointments set up here (all free through tricare). My husband was going to do the medical and I was going to be the shopper (I could have gotten each pair of glasses (regular and sunglasses) for $250-300 given he doesn't need fancy lenses). She demanded child be sent home next day and then finally scheduled the appointments (it was bad as he told me April the day before he was leaving on Spring Break that he couldn't see well and come summer she still hadn't taken him - my husband mentioned it to her and offered to pay for the glasses/lenses if money was an issue - given we both were glasses we are very sensitive to it).
Sadly, we had to give up as when we tried to do that stuff, she'd refuse, upset the son and make him come home. The only good thing is she is very competative, so then she took care of the glasses - not what I'd get, but at least she got them. She also only bought new clothing the day before our visits (since I always overfilled the suitcase with clothing for his return trip)- I liked what she bought, but she didn't ever buy enough. I wish there were ways around it as he really needs braces too. But, the only way to deal with it is through court, and if we fought it between attorney's and travel costs, we couldn't afford the braces, glasses and other stuff. And, braces are court ordered but for what ever reason she will not get them put on.