Thank you for your query.
I suggest that your daughter be examined by the doctor, preferably an orthopedic surgeon, who will see her posture and try to find a cause for such a posture. Depending on the examination investigations may be ordered to rule out any spinal cause for the posture. Physiotherapy
may be suggested to correct the posture and/or strenghten the back muscles so that your daughter stands upright.
Exercises and gymnastics are good but should be done under guidance so that the back is not damaged.
I hope I have answered your query to your satisfaction.