Mail defaults to the wrong Reply To address

I’ve got a strange thing happening in Apple Mail (15.0) on my Mac (OS 12.2.1) that I can’t figure out. When my wife emails me, my responding email back to her always defaults to a different sending address (one of my others — the same every time) than the one than she addressed hers to. This requires me to manually switch the “From” address each time. 

This doesn’t happen with any of my other addresses or people. This also doesn’t happen if I initiate an email to her. In that case, when I address the email, Mail defaults to using the correct sending address. But it will happen if I send the original email (using the correct sending address), then she responds back to me, and then when I respond back to her, the address once again defaults to a different sending address than I originally used.

In case it matters, this is happening with Comcast addresses using IMAP (however, the address Mail keeps switching me to is not an Comcast address and doesn't use that same server). I pretty much only use this particular address with my wife and daughter and only have this issue with my wife’s emails.

I’ve checked all the settings I can think of and it seems there must be a rule set somewhere that I haven’t found that is causing this. Anyone have any ideas?

And if the above wasn’t clear, here’s an example of what I’m talking about:

Wife emails me to me@example.com

I respond to her and instead of using me@example.com, Mail changes it to me@example2.com