You know, I'm wondering if you should bring up the counselor talk again...then, when she says no to going... then bring up the fact about the note you found, the book left in your daughter's room about D, also, the endless "private" phone calls...accuse her of having an A, be it EA or PA and that you will not stand for it. If she gets a little defensive, then, tell her that her behavior is just that - unacceptable.
Maybe, you need to force the issue and "break" her down. This would be confrontational, I know, and that you do not like to do that...but, Luke, maybe it's time to be super aggressive and take charge of the M now...you steer it for a while...you tell her where you both will go, do, see with the kids, etc. See how she reacts...if she yells, yell back...