Would you respond to this email?

My ex-husband uses his facebook account primarily to bash me and recently he has friended several of my old friends. Yesterday after he put up a particularly savage and for the record untrue post about me I received a very chatty “just checking in” kind of email from one of these friends. When we lived in the same town this was one of my closest friends but since moving and my divorce we haven’t kept in close touch and she knows none of the details of our break-up – which has turned rather ugly. So do I respond and tell her that she is only getting half the story? Respond and pretend as if the post wasn’t there? Ignore the email? I am kind of tempted to share the whole story just to stand up for myself but I am not sure it is worth the effort.