Since you guys have been together for SO long (and since you were both so YOUNG), I hate to say it but she's going to have to figure out what it feels like to be without you before she's ever going to be "all in" your marriage again. With no kids involved, by advice would be some variation of the "set them free" method, going completely dark, and doing Michele's after-the-LRT technique.
If you smother her, it's going to completely backfire. She needs to know you HEAR her, and that while you don't agree, you do respect her decision right now.
Of course, you WILL have to set boundaries as part of that (she should move out, or at LEAST move into the guest room and no just coming-and-going at all hours of the night . . . you shouldn't pay for ANYTHING that she uses to conduct her affair(s), etc.).
If I can find it, I'll post a link to some old "Set them Free" thoughts by an old poster around here -- there's some excellent stuff in there. It's basically just a harder-core version of MWD's "dropping the rope" mixed with her "after-the-LRT."
