I have a few things I can add from my dealings of my wife who thought the grass was greener.
1.) she too went through a period of depression (actually 2)
2.) She ended up cheating on me
3.) She used to give me crap about me signing up on facebook. (I never chatted or received emails.) She later signed up and began chatting. ALOT
4.) Cell phone bills through the roof.
5.) Lots of going out with her cousin
6.) Lots of us arguing during the summer as she was constantly on the phone and at times even taking off at family parties leaving me with our kids to hang out with her cousin.
7.) later learned she wasn't spending that time with her cousin.....
8.) I allowed this behavior as I didnt want to rock the boat. I hated fighting.
9.) After Thanksgiving of last year, I became deeply depressed. Over our relationship, finances and the upcoming holidays.
10.) New Years Eve, Probably the best day of the year for me. Wife and I spent the whole day together. Intimate that night.
11.) next day. Made breakfast for the kids and for her in bed. We ended up watching a movie though she didnt come downstairs right away. She was talking to her cousin. She had to go to work. Sent a text to her on her way to work. She responded right away. Sent another. Again responded right away. I thought it was fishy and sent her one more text saying why are you lying to me and that day we separated.
Why am I telling you this? Lots of reasons. One, facebook can lead to many things. I wouldnt trust the flirty emails or chats or text. Not at all. As others have said, and how my experience makes me feel, red flags are present.
As for counseling, you are doing the right thing. If it was her decision to separate, then who cares if she get's upset at you for getting help for yourself. If she didnt find it helpful, too bad. I've said this to many people on her. Learn this phrase (This isnt meant as condescending). "I'm sorry you feel that way."
If she doesn't want to go to couple's counseling so be it. However, the best answer I can give you for what you want for it is this: I was hoping that you would attend as it could help us communicate better in our marriage. But should it for whatever reason not work out, I think its important that we both have a way to discuss together how to communicate to our kids what is going on between us."
As for the stringing you along. This would only be happening if something is going on behind your back. Not sure if have access to her computer of its the family computer but if you have a chance, I may have an option to capture some "chat sessions". It may only capture the messages she sent (I cant remember). I used it after the fact to confirm when my wife's affair ended to make sure she was telling the truth.
http://www.jadsoftware.com/go/?page_id=225
Feel free to ask any questions or follow up questions on any information. I have no problems sharing my experiences.
I especially agree about never leaving the marital home and bed if possible.