Oh my-I must read that story:)
(There is one thing that trips me up in the "Susan leaves Narnia because of sexuality" idea; the first King and Queen of Narnia were a cab driver and his wife, King Frank and Queen Helen--so,while Lewis certainly has quite a few chips on his shoulder, it doesn't seem quite that simple to me--it's well worth noting, of course, but it seems like there's a lot going on that isn't just Susan)
I think the allegory is all about Mithras anyway:)