I really can't imagine how you stay sane reading her e-mails. I have written my OM the most worshipful, detailed, romantic, erotic stuff humanly imaginable. My H would probably NOT have had the strength wait this out had he been reading my e-mails. He saw just the subject line of one one time, by accident, and was mortified.
You say " I want to have this knowledge so I can determine how I need to act around her." Bear with me... so you are saying, if she is being a certain way with him (say romantic, or hesitant or upset) you THINK you know just how you are supposed to react to that for maximal strategy effect??? Well, even if you are a savvy manipulator (which you sound like!) I don't think people are that predictable or easily manipulated. Too many other variables involved! I think you know that and are just being plain old nosy, quite frankly. Mark my words... one day she is going to say something to OM that is going to be so painful to you, you are going to have trouble accepting it, your W, and your M. That seems like self-sabotage to me.
"I will be out of town much of this month, and she'll be home with the kids and her girlfriend who says she won't be accomplice to any kind of meetings or romance between W and OM."
You being out of town... THIS IS VERY BAD TIMING! Your marriage is at stake. On the brink! Isn't there ANY POSSIBLE way you could be with her for at least three steady weeks after she (supposedly) wraps up with OM? This is critical...
Go to a web site called "Marriage Builders" ... Dr. Harley recommends that the W spend MAXIMAL time with her H right after break-up with OM. And that the H make maximal effort with loving gestures and positive, complimentary veralizations at this time. It considerably reduces the risk that she will fall back into contact with OM!! Remember, ... every time she falls back (recidivism) it makes it that much MORE likely she will fall back AGAIN the next time. Because recidivism is a habit in and of itself, in addition to the habit of the affair! You really need to be by her side at this time, that's my two cents.
I don't think people are that predictable or easily manipulated. Too many other variables involved! I think you know that and are just being plain old nosy, quite frankly. Mark my words... one day she is going to say something to OM that is going to be so painful to you, you are going to have trouble accepting it, your W, and your M. That seems like self-sabotage to me. 
