1,095. Preparing for Immersion

159:10 If a bride saw blood before the wedding, if waiting five days would place the wedding before she goes to the mikvah, and if postponing the wedding isn't feasible, then she can make a hefsek taharah immediately, before twilight on the day she stopped seeing blood. She counts seven clean days starting on the next day so that she can go to the mikvah before the wedding.  This is far preferable to holding the wedding while she is ritually unclean.

160:1 On the seventh day, while it is still light before twilight, the woman washes her entirely body thoroughly with hot water, particularly her genital area and areas where there are folds and creases. She should check her whole body wherever she can see and feel with her hand to ensure that nothing remains on her that could create an interposition ("chatzitzah") between her and the water of the mikvah. She should also wash her hair and comb it thoroughly so that it won't be tangled or knotted. This is called "chafifah." The woman should perform chafifah until it gets dark and immerse in a mikvah immediately afterwards.  Optimally, chafifah should be performed right before her immersion and also by day. Therefore, the proper practice is to start chafifah while it is still day and to continue it until night.