This issue does nothing to assuage my sense of ambivilent dissatisfaction with Gail's handling of Diana. Quite apart from the massive OOC douchery involved as you've rightfully pointed out, the denouement we're presented with here doesn't even feel faithful to the initial premise of the relationship.
This is Diana, the woman who binds herself in her lasso every morning to strip away the falsehoods of her own existence. I can buy her genuinely experimenting to see if she can build something with an ordinary but worthy mortal man and hoping that it will work but coming to the ultimate realisation that there just isn't the necessary spark there.
But not this.
Her little Cornellian speil at the end was another thing about this issue that rubbed me the wrong way. It just feels wrong.
And I'm still waiting for an explanation behind the Spiked Eyemask of Fail.