How incredibly frustrating.

My thought is that pretty much anything you do at this point is likely to make it worse. You need outside help. If that can't happen for a while I think your best bet would be to push the pause button. Be honest with your daughter "we are worried about what is happening and we don't know hot to best fix it. We know you are capable but something about the way this course is set up just isn't working We know there are answers out there that will get us all feeling better but we need to get help to fine them."

Meanwhile if you haven't already done so I would explore what kinds of options you have available for the "pause" button. Can she take a "w" or an "incomplete" math and start again with a new strategy and new supports in the fall?

Have you looked into the possibility of a phone consultation if travel is out of the question?