Of course not, but I don't see how that changes anything. If you mean that Lewis deliberately chose to have Susan turn apostate as part of the story in order to make a particular point, of course you're right; but as I've said, there's nothing unrealistic or untrue to reality about either the fact that she does so or her motives for doing so. We may say to ourselves, "I wouldn't have written that," or "I would have written it differently," but that's a different issue, a matter of subjective taste and opinion. Not the same as alleging that Susan's abandonment of Narnia proves that Lewis was against sex and/or a dreadful misogynist.