I thought this was an interesting piece from Yahoo, a stepmom talks about her decision to disengage from trying to co-parent her teen stepdaughter because it was turning into such a manipulative and negative situation.  

Making the choice to disengage as a step-mom can be very difficult. It may seem like you are giving up on the child, but if the child is not going to give you the respect you deserve as a parent and is going to continue to manipulate and disrupt your family it may be the only choice available. Disengaging, gives you a chance to save your sanity and allows you to focus on the rest of your family. Sometimes you have to choose what is best for the family as a whole and not just one child and all you can hope is that it will make a positive impact on the child and they will realize the difference between right and wrong.

You can read the complete article at: http://voices.yahoo.com/the-disengaging-step-mom-it-1576363.html

How do you feel about a stepmom disengaging from a parenting role?  Does your opinion differ if you are the birth mom, would you prefer that the stepmom disengage in this matter?