AS, difficult to find out about her cancer this way. I hope things work out for your W.
Sometimes snooping is useful, to see where your W is mentally. The downside is its affect on your PMA, GAL, and 180's. The fact that she does not proceed with D says that she is still undecided. However, it seems that as long as the OM is in the picture, then reconciliation will not happen either.
Also, I think it worthwhile to remember that you W might be "trying out ideas/feelings" on her friend, and everything she writes is not necessarily how she feels.
Once she tells you, you need to support her. My guess is that 20 years counts for something and she will welcome both emotional and other types of support.
