Hi there...Most probable reason of lower back pain is spine disc herniation. Especially if the pain radiates to the leg and travels through buttock...If she has frequent urinating, burning while urinating, kidney infection can give back pain as well...hence get clinical examination done once with your family doctor they will guide you further.

Hello there.  I can understand your concern.  There can be many problems that could be causing the pain as already mentioned by my colleagues but they have forgotten about calcium and vitamin d3 deficiency.  This is most common in females these days. Tab. Supracal pro once a day after food for 3 months.  Tab. D3 must 60k once a week for 12 weeks. Tab. Health ok once a day after food for a month. Get her checked out by a orthopedician in person for further evaluation and management. Best regards. Dr. Anil kumar jain. Bangalore.

Postural problem...need to educate right posture while sitting...meet physiotherapists

Hello....... Lower back pain could be due to paraspinal muscle spasm , intervertibral disc bulge or herniation,damaged bone or ligament,radiculopathy..if her job requires to sit for long period of time that could be the reason. Improper posture puts pressure on spine.. Try physiotherapy.