She is feeling guilt .. she knows what she is doing is wrong so she is turning to you for the emotional support .. this is not the first time I have read you saying she has done as much ... and you have been setting the boundary and letting her know that support is gone.
I did the same with my W, was a point she needed me to take care of her, she was ill and when she would feel that way I was always the one she would call ... 2-3 in morning, wekeends .. you name it ... well right about Christmas I dropped off S, she was on the couch all sicky .. asked if I would go grab her some things ... I smiled and said sorry I have plans .... call OM I am sure he would be more than happy to be 'that guy' seeing how you both are 'soulmates'. (I was more happy I pulled this off without straight up laughing my a$$ off) Turned out to be a tipping point in my sitch ... she and I both knew OM was not that guy and never would be.
Keep at it .. you are doing well .. I know it hurts, but you have to focus on the big picture here.
