Don't worry. The change in your daughter's vision is common. I suggest your child to have eye examinations once a year. Their eyes are under development and can change more quickly than adults' eyes. So eye examination is especially important for them to prevent some potential eye disease from happening or notice any changes in their eyesight.
Well, This is common for most children. Their prescription may change following a growth spurt. Maybe they just spend too much time doing their homework, watching TV or playing computer games. I suggest you to remind your daughter to form a good habit of using eyes in daily lives and take care of her eyes. Besides, you may need to buy her a pair of new glasses immediately.