Alimony, which involves financial transfers from mostly men to women after a divorce, has recently received more scrutiny in the United States by members of an emerging social movement. These activists are attempting to change alimony policy in ways that economically benefit them. One important part of this movement are second wives, who ally themselves with their new husbands and against first wives in the pursuit of alimony reform. This analysis examines how these second wives articulate their objections to alimony by introducing the concept of economic boundary ambiguity, meaning in this case, a state of human relationships where financial obligations between first and second wives are contested. In addition to creating several tangible stressors, economic boundary ambiguity can also have important consequences for women’s own social identities as well as the collective identity and the success of the social movement overall.