we do share a bond, i spend at least an hour with her each day. I'm trying to spend a lot of time with Lily and still spend some with the new girl. As far as caging, i'm lucky because i am a wildlife rehabilitator..that means i have tons of empty cages at this time. I have only introduced them on 2 occasions. Both on my bed with a hand on Lily. She will sniff the baby for a while, then make a move like biting, so i have yanked her away each time, and then it starts over. I don't know if she actually bites the other rat, or if it's just like when she grabs something... I would leave them to find out...but the new rat is SO TINY, and i'm afraid Lily could kill her very easily, and she doesn't have much for teeth. I bathed them both, and gave them each the others' drying cloth, for sniffing, and each day i will introduce them again. I'm a little confused because if Lily was obviously mean, then the baby would fear her, right? Well each time the baby hides, but then ventures back out after a few seconds.