Can I ask what you hope to gain from this?

She's not going to respond. If you're going to send it anonymously, perhaps you don't even want a response?

It might even adversely affect the complaint against her (which I imagine might be more healing for you if she is disciplined, as she should be).

I just can't see how it would bring closure or healing.

I get the giving yourself a voice, but how satisfying is communicating to someone that they hurt you when they may not even read your note or poem?