Lazy eye is a condition that is fairly common early in childhood and it is important to see a pediatrician or eye doctor as soon as possible. It is most commonly caused by misalignment of the eyes, but it can also be caused by problems with the passage of light into one or the other eye. When there is misalignment or unequal vision in the two eyes, the brain preferentially uses one eye to process visual information and neglects the other, allowing it to "wander" and not focus on the objects under scrutiny. Lazy eye is commonly diagnosed in younger children, and it would be unusual for diagnosis to be delayed until 12 years of age. I think this actually makes the urgency of having the eyes looked at by a doctor even greater, because it raises the possible that some rapid deterioration in vision might be behind the problem, if indeed it is confirmed. I would suggest going to see your pediatrician or an eye doctor as soon as possible. They will be able to take a look at your daughter's eyes and vision and help figure out if there is any defect in eye alignment or in visual acuity. If any problem is detected, they'll be able to help guide you regarding what to do next.