WTBH, what she did was wrong, but I doubt it is grounded in the calculated malice you're attributing to her. You can say, "She had to have known" how it would affect you, but I doubt she is thinking clearly.
I'm not suggesting for a second that you should welcome her back into your life after this, but for your own sake I think you need to consider what's real, here, and what is a product of you own (perfectly understandable) reaction. What's real is what she DID, what might NOT be real is what you think her motives and thought processes were. She felt attacked (wrongly) and she tried to retaliate (also wrongly). I doubt she was thinking, "Now, how can I retaliate in the very MOST hurtful way possible?" It sounds like a knee-jerk reaction. That doesn't make it right but I doubt that you misjudged her all those years and befriended a monster.