There are various reasons for lower back pain. Did she had any injury or jerk.
The most common reason for lower back pain in this age is due to muscle spasm of lower back muscles alongwith decreased bone density..
Next Steps
I will suggest to start with hot fomentation, take analgesic with muscle relaxant tablet, apply analgesic ointment 3-4 times daily..Take bed rest for now
Health Tips
Avoid heavy work for now. Also avoid sitting down, avoid Indian toilet, avoid forward bending, avoid stairs..