Q. Can a woman who is about to convert and go to the mikva, do so if she is a nidda? Or does she have to purify herself first? If she feels that she wants to be totally tahor and pure before accepting the Torah and mitzvot, should she immerse for nidda also?
Is she required to study the Laws of Nidda before conversion?
A. Horav Shlomo Miller’s Shlit’a opinion is that she can convert while being a nidda, as has been done throughout history. There is also no point to be tovel for nidda impurity, before the immersion of gerus takes place, since at that time, she is still a Gentile and the nidda mitzvos and effects do not yet apply to her. The tevila at that time will not make a difference, on her nidda status. One should add, that our tradition is that unmarried women do not immerse in a mikva.
See question 942 regarding a married couple that convert together.
She also does not have to know the laws of nidda, until she is ready to get married. However, she should know the basic principles involved, as part of her acceptance of mitzvos at the time she converts.
She should also know well the laws of chatzitza or barriers to immersion, construed by substances that interpose between the body and the mikva water, as they are essential for her proper gerus immersion.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a