Where to begin? Part 2

[Cole_]

would someone who is intent on leaving the marriage want to go to a birthday party which will have my family there?

I think the better question to ask is "Does it matter?".

Focus on yourself and being a better man. Try to stop worrying about what she is thinking or what she is doing or what her motivations may or may not be. IOW, detach and simply go with the flow. Listen, observe, but try not to concern yourself with what she is doing and why. Notice what she is doing, certainly, but don't let it change your focus and don't let it distract you and get your hopes up. This is a marathon and you don't want to run off chasing the rabbit.