Steve, Yes, Cara could be "right on" with conflict #1, as I read it at least. Conflict #2 if considered on an emotional level could explain her warning to you, that further involvement with Robert could cause her to, "cut you off" sexually, except with condoms, as she has already suggested.
My previous post centered around Sue's statement: "I guess you want this to happen." I have to think that If I were asked that, about a matter as serious as this, It would be time to come to a mutual decision. Not throwing it back, by effectively saying, "What ever you want is OK with me."
Maybe it's just my impression, (well not mine alone, from what I read here) but it seems to me that Sue is very worried about what could happen to her relationship with you, if she gets deeper into her 'affair' with Robert. As I said, she knows him intimately better than you do.
Again, It seems to me that she is reaching out for your 'concern', and you just are not showing it, at least not the way she would like you to.
I realize that my impressions are all 'third person': Sue - to - you - to me, through this forum. Certainly everything from your communications don't come through clearly, or are possibly mis-interpreted. I respond to what I believe I understand, colored by things like experiences, mine and others, and what I know of human psychology.
certainly, as I have read every thing you have written, (more than once) I believe, at times that I can feel the emotions, both yours and Sue's in the words you write. My feelings in that regard, have been right more than wrong.
When others, with even more experience than mine, have the same conclusions, I feel justified to make my thoughts known. Not to irritate you, but to advise you, as I would any other of my friends.
Thanks for listening, Harry