Dr. Asher Meir addresses a very tough question in his Jewish Ethicist column (link):
Q. My husband has recently become much more observant, and he is pressuring me to transform my lifestyle as well. How can we move forward when I really want the old him and he seems to want a new me?He doesn't directly address the "big one" -- going to the mikvah -- but he makes his answer clear:
An instructive source of guidance is to see what kinds of behavior are considered in Jewish law grounds for divorce. It makes sense that if a behavior is considered grounds for divorce then we would say that the spouse has a legitimate demand that it be changed.Feeding your husband non-kosher food -- that's not going to the mikvah. I don't know how couples deal with this but if you love each other you won't object to being inconvenienced, even in a significant way. I give a lot of credit to people who become more observant later in life. It certainly requires many lifestyle adjustments but I guess that's the point.
We find that in general, a spouse's conduct is grounds for divorce only to the extent that it impacts the other spouse. The Talmud gives the example of a wife who feeds her husband non-kosher food. The fact that she herself may not eat kosher is not mentioned...
It is reasonable, within limits, for you husband to expect you to accommodate changes and enable the "new him" to adjust his identity. But it is not reasonable for him to expect you to substantially change your behavior or identity. Acceptance is the most basic precondition for coexistence in a marriage.