He dosen't have to manifest through her, he just likes her for some reason. It was Mukuro's coaching that got her through the fight, otherwise Glo would have killed her easily. And she may be able to make her own organs now, but she can't do it without being comatose, which negates her usefulness. Don't get me wrong, I like Chrome, but she is only able to keep up with the boys (but rarely does so), because of Mukuro. Bianchi tried to train Gokudera, but he quit on her. Sistema CAI was all him. Lal is the most badass, and would be on the level of Hibari and some others if it weren't for her AIDs. I honestly debate whether she survive the future arc.