We appreciate the sensitive nature of this question.

Barring very extenuating circumstances, a couple without access to a mikveh on mikveh night would typically be instructed to delay immersion.

The seven clean days cannot be shortened, and a woman cannot immerse before completing the clean days. Couples who follow Ashkenazi halachic rulings cannot shorten the five-day minimum wait.

In very extenuating circumstances (e.g., established fertility issues, where one day might make a difference), a woman may be permitted to perform her hefsek taharah on day four, or to immerse during the day on day seven with restrictions on seeing her husband before nightfall. Please get back to us with more details if you think one of these rulings might be relevant to your situation.