The pain obviously shows all signs of a neurological origin. Do not go into extension patterns in low lumbar areas as it will only crunch up the nerve and make symptoms worse. Try ease off the pain first then progress towards improving her core stability by multifidus and Transversus Abdominis facilitation.
also try the 90-90 position of hip knee flexion for immediate relief of pain. Wikipedia reference-linkSpondylolisthesis should have a traumatic cause or if the patient is old and osteoporotic then you can start suspecting it.