Perhaps if you can do some internet research about being blind and show it to her, she might start to understand how valuable her eyesight is, and learn that if she does not take care of it now, by the time she gets to become an adult she may well already have caused serious damage that will not be capable of being undone. As a lighthearted exercise, try and get her to wear a blindfold in the house for a couple of hours (with no cheating) and ask her to tell you how it feels. She's a little young to start thinking about such serious issues, but it may help her to understand why you are so anxious that she protects her health now.
Also, try and ensure that she has some really fashionable glasses rather some of the rather dreadful NHS frames which are available. This may be an expensive option, but if it encourages her to wear them, it will be worth it.