Well, If the talking was before she met him and then she stopped all contact afterwards then that is even less for you to worry about because she didn't keep talking to him afterward. It was a one off just like your blow job was and that's that.
If you can't get over this then I suggest you talk to a personal therapist and dont worry about her going with you. This is your issue anyway and it's you that has to come to terms with what happened.
If you're not in depression now, then clinging to your thoughts of this will certainly cause you to be depressed. Seriously, do something productive and go to your doctor for a referral or start on that aversion therapy. You just keep coming back in a justifying why you should be in this state instead of even considering or at least trying some suggestions you've been given to help yourself to get mentally past your OCD thinking on it.
So: What are you going to do to help yourself? Lets here some of that now.