I feel for you today. I think after we have been through betrayal it doesn't take much to trigger it and then start questioning everything. I have done it numerous times. She could be feeling some of that apprehensiveness in you? She may have some guilt floating around and not know how to address it and the mug just brought it out?
You sound like you are happy and you both are doing great trying to repair your lives. There will always be those issues in the background. One day at a time. I hope you have a better day today.