Your Grandmother Was Right
Every Indian kid has memories of being pinned down for a champi (head massage with oil). We hated it then. Science has vindicated it now.
Coconut oil is one of the only oils that can actually penetrate the hair shaft (most oils just coat the surface). It reduces protein loss by up to 39%, strengthens the hair from within, and the lauric acid in coconut oil has antimicrobial properties that keep the scalp healthy.
A 2015 study in the Journal of Cosmetic Science found that pre-wash coconut oil treatment reduced hair damage from combing by 62%. Your nani knew this without the study.