I don't like what you T is doing. This kind of a dual relationship is not unheard of, but this is the first time I hear a T being so stubborn. If it is just regular religious stuff, I don't get the problem. A normal thing to do would be discussing beforehand how to act if meeting there. Like if there is greeting ok, discussion no or whatever feels right. And to have a plan what to answer if someone asks if you two know each other. Maybe a vague "from work" or "through someone".