regardless of her prestiged childhood, she did something wrong and feels that she has "paid" for it, and now she doesn't want to talk about it anymore. and most certainly does not want to be "guided" by you on how to be faithful. she knows, she just has to put it into action, and she needs to test her various methods, if you will.
she put her fidelity in a MOST precarious position before and she definitely learned something from that experience
i know the books say she has to be the "giving" one here, (I have a lot of thoughts on that, not too popular, but then again, i'm not the lbs, so...)
i think, that you have to let her answer to her own conscience on that...
all you can do is voice your fears and feelings and let her conscience do the rest of the work. the more honest you are with your feelings, and only yours (no blaming, no predicting), then she'll be allowed to be honest with hers.
does that make any sense?
see, if she's mad... she have a reason to *talk* to this single man friend, seek support, comfort, advice... just friends, promise... and then... she gets mad again... more talking...
listen, i know this is unacceptable behavior, and if you DON'T accept it, you can keep starting fights about it and wreck your M... you know? if you do accept it, and convey your true self in the most gentle way possible... then SHE can come over to YOUR side... you know?