Hmmm...seems like she is thawing a bit. She is initiating convo's with texts and talking about her feelings. That is good.
I would just say I am sorry to hear you have been sick and leave it at that.
As for her statements about not telling people in her office about the affair and romance, I would not respond to that either.
I view both of these statements as "bait". She is testing you and how you respond will give her the assurance that you still care and are there for her while she is with her other man. It would only lead to an argument if you responded anyway, right?
My suggestion would be to continue to stay as radio silent as you can be. That is the most powerful "weapon" you have in your arsenal.
