Hi
I am not positive on what you can do. She might be trying to dominate the others or she might be protecting you.
Is your little one on the floor when you introduce her to other dogs.? I found if I was carrying Jackson he would be very growly etc with them. If on the floor however he would not be quite so brave.I found the worst thing I could do was to pick him up and carry him with other dogs around and new people around. Seemed to give him more power.
We are in an art group that bring little and big dogs so we just let him walk in and he worked it out with the others as we knew they were not nasty.I would not do this with dogs I didnt know of course.
We got him at a year and a half and had him over a year now. He seems to be better than before.
I would say if she is on the couch with you and the others come around and she growls then put her on the floor so she is cant be so dominant over them.
I am sure you will get a better answer on this soon. I am no expert for sure.