I'm not sure why everyone automatically assumed that Layla's a boy instead of a, you know, bizarre doll. Undertaker had stated a while back that Polaris and Vega were out procuring blood for rCiel. It's been revealed that Polaris is the knife-wielding butler (and possibly a character we already know like Joker given how only part of his face was revealed), and that Vega are a pair of twin girls. Layla is definitely one of them, if not somehow both of them.