How do you do you address wife of a peer in a letter?

In a letter, you can address the wife of a peer using her formal title or simply by her name, depending on the context and your relationship with her. For instance, you can start with "Dear Mrs. [Last Name]" if you want to maintain formality, or "Dear [First Name]" if you have a more casual relationship. If she holds a specific title (like Dr. or Professor), it's respectful to use that as well. Always consider the tone of the letter and your familiarity with her when choosing your salutation.