So the action part of disengagement is going fairly well - not trying to fix things or parent SD, spending way less time with her since she does an after school program instead of being babysat by me. It's made me a lot happier and less resentful since I dont need to bend as much of my life to suit her. I still find her incredibly obnoxious when she is around but its much easier to tolerate for shorter amounts of time.

The mentally disengaging part is much harder though. I still am expending way too much mental effort fixating on her behaviors, DHs reaction to it, etc. I still have quite a bit of anger about past incidents. Theres also alot of guilt about disengaging. Some fear too that I will be blamed when things go wrong. MIL is already blaming everyone else in the family for SDs problems (me and my son and the baby are taking attention away from SD and DH neglects her according to MIL) and I feel like other people will too because SMs tend to be the scapegoat. In reality when SD is here she demands everyone's attention so she gets a ton and her behavior was abnormal already when I met her. DH just didnt realize it yet because he wasnt around other kids much and she hadn't started school so he didnt get that feedback from her teachers. 

Anyone have any tips for dealing with the mental/emotional part of disengagement? How not to feel responsible for everything all the time?