I really have to agree with Puppy. Remember that most (if not all) WAS's are cake eaters. They want it all. Of course she wants your friendship for several reasons: it shows that you are ok with what she is doing and validates her actions, it will make things seem ok to the kids, you will be there for her on the back burner if things go bad with the OM, and you are someone she's had in her life for a long time, so losing that completely will be hard for her. Be very careful with what you are thinking your W's actions mean. I've seen this same behavior with my W and it's led to nothing more than her saying how great we are as friends but that she's just not in love with me. Don't let your W eat cake. Remember that gluttony is a deadly sin!
