Try a chiropractor, back pain is different for everyone so it may be as simple as poor posture that's contributing to her pain. A simple way to see if the spine is out of alignment is to have her bend over and touch her toes, than you can run your fingers alone the spine to see if it's straight.
When the spine or other bones are messed up, this interfers with the nerves.
Never believed in it myself...Until the pain got so bad...Then I had to try it.
And so glad I did, the first appointment brought immediate relief...It's like a dam had been broke and I could feel the blood and electrical pulses moving through my body.
Good chiropractors can be found by word of mouth. :)