I wouldn't work somewhere where people were abusive to me about my work. Not even if they paid me. On my way out I'd drag HR and the lawyers in to it.
To assume someone should accept that in a voluntary position is just fooling yourself that they'll stay.
And to anyone saying she is being a bit thin-skinned, it really doesn't matter, the law matters and when it catches up, which it will, she'll be a thin skinned volunteer with the law on her side. She walked away, she isn't the one to worry about. The one to worry about is the person who is collecting a dossier of all those abusive emails with an eye on suing you and taking your business off you when the law does catch up.