[Lil Sis]

Sophie must be going after Allie because she can. The other girls won't let her.
I don't see Allie as the "pack leader" if she is afraid.

I can only tell you what has happened to me, but it is with males so would be different. .

So, if Sophie is really aggressive it may be beyond what you can change by yourself. If it is a more simple puppy play role finding you can discipline. Sophie must not be allowed to bite (as you know) and I am thinking some behavior modification almost like a new puppy that doesn't know not to bite???? Like if a puppy is brought home too early? Sophie must learn empathy.

I hope my ramblings have helped