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most likely she is suffering from sciatica due to slipped lumber disc or narrowed spinal canal
.For pain you may try, painkiller such as indomet or ibuprofen
for a few weeks.If it does not relieve her consult a neurosurgeon and have a MRI of dorsolumber region.It will reveal the site and nature of lesion and direct anticipated management.
For self care avoid bending,weight bearing and strenous exertion.Do the daily activities within limit of pain.