I think you need to make it clear, in plain words, that you are not willing to be a part of a 3-way relationship (Her, You, Him). Tell her what YOU can live with and what YOU cannot live with. If she values YOUR friendship and YOUR support then she will need to make a choice. You are right, she needs to make it, but she never will never end this affair (EA/PA/Whatever) while you continue to offer tacit support for it with your silence.
H: 38 W: 36 S: 8 S: 5 M: 16 Bomb: 8/25/08 OM: 9/21/08 EA (Possible PA) with co-worker since 5/08 (at least...) Sep: 9/21/08 D Filed 9/23/08 My Situation