What impressed me with Lily was the fact that she wasn't going to waste time bonding with us! We were allowed to cuddle and kiss and smooch with her, but she wasn't going to invest with us beyond the basics. We didn't favour one over the other in the short time we had custody of both - that would be cruel and pointless, but she made it very obvious we were merely a means to an end. lol
I also think that with Bella being the more dominant of the two that wee Lily was taking a back seat while they were still together. Now that she has her own kingdom to manipulate, she has come into her own. Same happened with Sadie, my friends little Blue girl. She was shy until separated from Euro.