ToSmile, I think your biggest struggle is in trying to exert control over her. You only get control of one person in this life, and that is you! That is what I was trying to get you to see with your "boundary". Your boundary isn't so much a boundary as much as it is a directive. "Thou shall not bring friend to the house!" That is more the type of restriction you would put on a child, not on an equal.
And then the struggle with how she parents. You seem to try to control her parenting style, even though, at its root level, it is just different than yours. Is her style old-school? Sure. Could she be better at teaching them things? Of course. But unless it is truly endangering the child I do not understand trying to micromanage her to that level.
Even your "patience" of three years seems more of trying to exert control. I feel like there is more going on here. Her leaving for 2 months and returning was probably more about her needing a place to live and needing money to sustain her lifestyle than it was about really wanting to return. Especially based on the fact that she returned but has continued to push for a D. ToSmile, I think you have to decide if you are willing to live with her during this limbo period....with no control over her, or to push for D. I do not see a middle ground here. You are struggling because you want control over what you have no control over.
Trust me, I've been there! It is one of the hardest things to face, that you have no control over her, or whether you get a D, etc. But you are going on 2 years here, and you continue to struggle with control issues related to her, who she is around (IE this friend you have so much issue with), and how she handles the kids. It has to be exhausting for you!
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018