1,111. The Mikvah Lady

162:6 While a woman immerses, she must have another Jewish woman over the age of bas mitzvah standing by to ensure to none of her hair remains above the water. If she doesn't have another woman, her husband can fill this role.

162:7 A woman is permitted to immerse on Friday night if this is the actual time for her immersion, so that she wasn't able to immerse earlier, and if her husband is in town. If her husband is out of town or if she could have immersed earlier, then she is not permitted to immerse on Shabbos. There are numerous factors when it comes to immersing on Shabbos after giving birth, so an authority must be consulted. If a woman's time for immersion arrived but she didn't go to the mikvah because her husband was out of town and he returned on Friday, some places are strict and do not allow her to immerse on Shabbos. In a place where there is no set custom, one need not act stringently. In the places where the custom is to be stringent regarding Friday night, she also should not immerse on Saturday night. A widow who remarried is not allowed to go to the mikvah for the first time on Friday night because it is prohibited for them to have their first relations on Shabbos. Some authorities are lenient and permit it following Shabbos.