My grandma talked my uncle's ex wife into cutting her hair before they got married.

I've never heard of that. Many of the old timers I have known believe that a woman's hair is her glory. That flies in the face of cutting it off.

The only time I’ve heard of men wanting their wife or girlfriend to cut their hair seemed to have to do with jealousy that another man might look at them. My grandmother was 92 when she died in 1984 and she had long hair till she died, she wore it up in a bun most of the time. I have never ever heard of older people telling younger women they need to cut their hair when they got married. Many times it’s after a woman has a baby that she wants to cut the hair shorter because she has less time to care for the hair.

I think Grandma was just being devious.