Thanks for using JustAnswer.
This could be a few things - if she has not started menstruating, it could be the onset. Basically, it could be hormonal changes.
It could be Attention Deficit Disorder or a Learning issue.
She could be unhappy about something, or it could be a medical issue.
Or, it could be something else....
The only way to get to the bottom of what is going on, is to first - bring her to her regular pediatrician. Have them just do a regular check up. If nothing medical shows up, then have her evaluated by a child psychologist. If that doesn't do anything to help - even with treatment, then consult a psychiatrist. It could be an issue that needs medication in order to get better.
Now, that's the long term plan - but for right now, check it out medically.
Then, psychologically, then psychiatrically.
Keep me updated - as she sees each of these professionals, and we can continue to talk about the next step.