In the book In the Time of the Butterflies, how does the movement impact Dede's marriage?

Although it might seem that the revolution causes the dissolution of Dede's marriage, I think that in reality it merely exposes weaknesses that are there already.  As Dede muses in Chapter 1, "If you multiply zero by zero, you still get zero, and a thousand heartaches".  Jaimito is a domineering character and believes that a woman should submit to her husband in all things.  In Chapter 9 he forbids Dede to become involved in her siblings' revolutionary activities, observing that "the Mirabal sisters (like) to run their men, that (is) the problem...in his house, he (is) the one to wear the pants".

Even before they are married, Dede knows that Jaimito "wouldn't give a rotten plantain for risky politics".  Showing no consideration for her thoughts and feelings, he pressures her to agree with his way of thinking.  Dede, "already beginning to compromise with the man she (is) set to marry", complies, even though if she "thought long and hard about what was right and wrong, she would no doubt be an enemy of state" along with her sisters (Chapter 5).

Although the revolution inarguably contributes significantly to the problems in Dede's marriage, in the final analysis her marriage fails because of deeper issues regarding independence and respect.  Dede remains with Jaimito until long after her sisters are murdered; when she leaves him, the days of revolution are over.