No, don't switch courses so fast...it just looks wishy washy. You can act "friendly" if you want though.
I wouldn't worry about what she wrote to her friend. She's not seeing you as anything but the enemy at the moment. My wife used to write stuff like that too. It happens. That's how your wife feels at the moment, if she takes an interest in you, it can change.
BTW, I think you need to do some things different if you really want primary custody. You can't be living at your sisters and only seeing the kids 24 hours a week. If she's the one watching the kids the rest of the time, you are really setting a precedence, plus, the court will want to know you can provide for the kids. You can't ask for child support when you aren't the one with the kids. There is also joint legal custody and joint physical custody. In the first, it's just semantics and doesn't amount to squat. In the second, you are sharing the kids 50/50 and generally the income of both is taken in to account and perhaps some awarded to the spouse with the lesser income. You can't get child support if you are just the spouse with visitation...that would just be alimony. So, could you clarify for me what you are shooting for? If you want to be the primary caregiver, you need to be establishing a home and having the kids the majority of the time.
You cannot be lonely if you like the person you're alone with. Dr. Wayne Dyer