Halachic practice concerning the immersion itself (e.g., how many times to dunk or when to recite the beracha), usually follows a woman’s mother’s practice. Aspects of mikveh observance that affect both husband and wife, such as the timing of immersion, usually follow the husband’s community’s practice.
In cases of need, there can be room for leniency. Please write back with more specifics if you think your situation might be one.