There is an inyan (not halacha) about covering your hair for a davar shebikdusha, but it obviously cannot be applied in every circumstances (think of a woman at mikvah). There are some women there watching who will put the towel over the head while she’s in the water, but it obviously does not cover things al pi halacha, but she’s still saying the brocho.
There are people who hold that the woman doesn’t have to cover her hair in her house at all and I know women who don’t, but I think that once you have children old enough to understand things, it is more problematic to have your hair uncovered except in the privacy of your bedroom with your husband. But obviously those women who hold that they can go in the privacy of their house with uncovered hair don’t hesitate to make brochos without grabbing a hair covering.