I’m with Meg Barclay, I think what your great-grandmother said resonates for some reason. It seems to make intuitive sense. After reading it, I thought “people cut their hair when mourning in the Hebrew Scriptures, don’t they?” and “penitents and monks shave their heads.” So then I went and googled “ritualized hair cutting” and found a lot about first haircuts, an interesting article about not asking women “WHY did you cut your hair” , and some hair folklore, but nothing about cutting your hair after trauma or to initiate a change.
There are a lot of people who don’t cut or wash their hair after someone dies, and then do shave, wash, cut after a prescribed period (10 days or something).
There are counter-examples, like Samson, where cutting hair leads to a loss of strength or fertility, but I can’t think of anything where cutting your hair “got rid” of things.
So, the best the Internet can give is what your great-grandmother told you. “We harbor our fears in our hair.”
I’ll probably be saying that until the end of my life.