Hi Bean,
you felt bad after sending the email, and you pinned your bad feelings on the act of sending the email. But what probably made you feel bad, was the whole shebang. The situation with your family, the fact that you had to block the emails, having to see the falsely happy email anyway, knowing that your MGP acts as if your blocking her emails is insignificant or did not happen, and then actually participating in your MGP's scheme of making you out to be the crazy one by sending an honest email, but one that you know the audience will construe otherwise. Then, the blaming started.
Maybe in your FOO all the craziness was blamed on you so you continue to attibute your bad feelings to yourself and your own actions. But your sending the email is not the thing you really deep down feel bad about. It's just what MGP would say you ought to feel bad about, and ignore her own role in it.
I think your venting here is wonderful and a role model to many of us!
Plucky