Concerned friend . .
I don't think you need our help or advice; you seem to have this well worked out for yourself. My (totally sincere) complements to you, and good luck to you and your unfortunate friend. The fact that she has friends/colleages like you does, at least, mean that the situation could be even worse.
Of course, if you overstep not only do you lose the friendship etc. but not a lot is achieved!
Beyond that, I think everything that can usefully be said has been said.
I'm sure the good wishes and kind thoughts of all of us here, whatever our opinions, are with you and your friend.
G.