Husband, Is this coworker someone you have had lunch dates with in the past? Are your lunch dates a routine? Does she know about your situation? Are you planning on telling her about it?
Honestly, why are you having lunch with her?
I think taking the ring off is fine. What does it mean for you? What is the message you're trying to send? How will it help you in your efforts?
If taking the ring off helps in furthering detachment, than I say fine. I know you're distressed by your situation, and I think anything that will lower it's power over you is a good thing.
CL
CL 53 W 54 M 20 yrs. 03'-09' Separation + Old Patterns + GAL 10-14' Piecing
"The Master allows things to happen. She shapes events as they come."