It's essential not to jump to conclusions in situations like these. Communication and understanding are keys to a healthy relationship. Begin by having an open and honest conversation with your wife about the situation. Share your feelings, and listen to her explanation. Consider that the situation could be a misunderstanding, and it is possible that she might have genuinely mistaken her cousin for you. If there is a pattern of suspicious behavior, that might warrant additional concern. However, if this was an isolated incident, trust and communication within your relationship should help you navigate the situation. Should you continue to feel uneasy, couples counseling or therapy could provide additional tools for fostering discussion and understanding in your relationship.