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A reply like that would certainly make you feel good in the moment. A bit of venting, a bit of retribution, a bit 'sticking it to her'. Unfortunately it would also just feed into the drama. It's not going to make her rethink anything, it's going to make her respond with even more passive aggressive 'non-judgmental' behaviour. She'll play the victim, she will talk to all your friends about how she tried to support you as a friend in a non-judgmental way and you responded in an aggressive manner that used to be "out of character". I'd also expect she would start to let slip your swinging as well, as further signs that "you've changed". That's a bit of mind-reading there. Might not happen, but a response like that would increase the likelhood of a situation like that manifesting itself. Much better to either not respond, or to respond in a nice way. It won't feel as good to you, but it's better for you.

"Advice on where to go from here with this?" I would send a short reply saying: "We will both miss both of you". And that would conclude the message. Signing it is optional.