Well, we know Dawn is an incarnation of the Key in the Form of Buffy Summers, or at least that's what I think it happening. My understanding is that the metaphor is between is that Glory represents a future version of Buffy, somehow. I don't think Passion of the Nerd really covered that, or I am unwilling to watch six years worth of episodes to find out if he did. So, a connection between Buffy and Glory would be the logical place to look for a connection.
In world, Glory and the Key have no connection, it's kind of like Loki sailing to Britain with a group of Vikings and deciding to steal Excalibur and the Holy Grail. Glory looks like that because that's how a Idol of the Flesh would look to humans, same as with Jasmine. Dawn looks like Dawn because of Summer's blood, and the key has to be pure, and not a vampire. So, the answer would have to be, it could be, but the show really doesn't give any indication one way or the other.