Assuming one thinks that she is a good coach one answer might be stupidity. It appeared that you are correct in that they deemed her to be too close to Miller and just wanted to wipe the slate clean even though I don't recall her ever causing them any grief even when her contract was not renewed.
the fact that they had two far better, proven candidates didn't have anything to do with it
Dartmouth is going against the grain, they couldn't find a US coach?
Maybe they know that after everyone else takes the pick of the litter there are no US players left, and they are hoping her connections in Canada can snag a few that Wisconsin, Harvard, Princeton, ... pass on.