i've located a nipping suspect

in the last few days, I've noticed bit tails, first just a couple, then a few more the next day.. and today someone took a bit more than a nip.. and i have a partial tailed rankin. I witnessed the smallest one grab hold of anothers elbow and really try to get a good chunk.. so i thought that was my culprit at first (then i realized that that was the first one to have its tail nipped).. so i inventoried everyone.. and found ONE perfect looking tail.
my question now is, i do not have room for another cage to separate it, and was wondering if i could possibly house it with an adult i have who takes no shit from anyone. i don't think she recognizes dominance at all. She is not aggressive, and i don't think she would hurt the little one,, but i also do not think she would let it get away with nipping. She is stubby tailed and minus toes already.
I'd love some input on housing them together? These are Rankins dragons. adult is female, baby nipper unknown gender.