Yehudahyonah, the Gemoarah does not say it is an absolute requirement for a mother of any Kohen Gadol. It just says it is a zechus to get there.”
We have had this discussion numerous times. I never read the Gemorah, I only learned this story in Yeshivah. It was the woman HERSELF who in RESPONSE to being asked why she merited to have so many sons who were kohanim gedolim, stated that it was due to the walls of her house never seeing her hair uncovered. That was HER belief. Did Hashem Tell her so, or did she make an assumption about something?
The Gemorah retells this maaseh to teach us about the great importance of tznius, yes, but IS what she said mamesh Halacha? I was not taught that it was. And perhaps she was mistaken in her belief in cause and effect. Hashem does not require a woman who is frum and ehrliche to cover her hair in the privacy of her home when alone with her husband (unless he is making a bracha). It is not meritorious for a woman to deny her husband the pleasure of seeing her hair, especially when it is ONLY permissible to him above all other males. It is not only a chumrah, but one which can cause marital discord, unless both husband and wife are on the same page about it.
BTW, we have been over this again and again. The story of Kimchis is well-known. But no one here has ever been able to prove to me that the story is meant to be taken as an Halachic imperative, but rather as a lesson of value.