Pullman totally gets it wrong about The Last Battle. Susan is not excluded from Narnia for sexuality, but for shallowness. The line says not that she is no longer a friend of Narnia because she is interested in lipstick and nylons and invitations, but because she is interested in nothing but lipstick and nylons and invitations. It is something which Lewis harps on a lot, what he calls "first and second things". That the "second things" may well be perfectly good things, but if you put them first, you end up truly enjoying neither the first nor the second things.

See Lipstick on my scholar for more details.