Good evening! I was contacted by a woman who has to go to the mikveh this Motzei Shabbat, which is the first night of Pesach. She doesn’t live within walking distance of one, and is wondering if she can go on Friday, or if she has to wait until Monday night. She already practices 4+7 due to fertility purposes, so there isn’t any wiggle room there. Is there any way for her to go early? I assume not, but I wanted to check because of their ongoing fertility challenges. Thank you!
I would arrange before Shabbat to have a cab pick her up after Tzeit Saturday night and drive her there and back. Once it is Yom Tov, the only problem with driving is making a new fire (i.e., the brake lights, turning the engine on and off, which is derabanan). Amirah LeNokhri for issurei derabanan is mutar bekamom mitzvah, so this would be fine. Just make sure that the driver opens the door so that there is no problem of the interior light.
In fact, if necessary in terms of getting back and not delaying the seder for too long, you can even have the cab pick her up after Shekiah. Even though it is still Shabbat and hence driving is a de’orayta, during Bein HaShemashot on Shabbat issurei derabannan mutar letzorekh mitzvah. (Shulchan Arukh OC 342 and Mishnah Berurah 342:2). Therefore, the derabanan of Amirah LeNokhri in permitted in this circumstance. Make sure to arrange the payment before Shabbat.
This would apply even regardless of fertility issues. Onah/marital sex creates makom mitzvah. As to going down to 3+7 – that is a totally different issue and would be limited to fertility issues and the like.
As to the question of going early, Friday is day 6, so it is not possible to go then. If we were discussing this a week ago, we could explore whether 3+7 were a possibility. Now, however, it is too late, since she did her hefseik taharah on day 4, we can’t start counting a day before her hefseik taharah.