Generally speaking, widening the jaw sideways is possible up to the age of 13–14 in girls and 16 in boys. Any specific age is only a very rough guide. The timing of growth varies widely, because children reach puberty at different ages, and this also determines when the jaws grow. In some girls the growth peak occurs as early as 10–11, while sometimes expanding the upper jaw with an appliance is still achievable at 18, for example.
This answer is for general information. Your own case needs an examination by an orthodontist.