She died in her sleep shortly after returning from Mount Arafat, according to her neighbours in the tent.
The 2,009 pilgrims from Borno, Nasarawa and the FCT, are from the 43,000 Hajj slots allocated to Nigeria by Saudi Arabia.
The medical expert said abstinence from food and drink enables the body to detoxify itself through the liver, gastrointestinal tract and the kidney, supported by the lungs and skin.
Mr Hassan urged intending pilgrims from Nigeria to be law-abiding whenever they were in Saudi Arabia for Hajj or Umrah.
Buhari has performed the Umrah (lesser Hajj) at the Grand Mosque in Makkah, Saudi Arabia, alongside Isa Pantami, Aliko Dangote, Wale Tinubu and Abdulsamad Rabiu.
The Nigerian leader urged Muslims to reflect on the historic significance of the Hijrah and the overall teachings of the Holy Prophet.