Chickens are pretty random in all things, so size won't determine pecking order. I have a couple more petite chickens that are EEs and they are all low in the pecking order, my small Black Astraulorp is a total spit fire and holder her own. She's not top hen, but she doesn't take much from the...
I've had a few that were slow to grow, one was a BA and ended up more petite and feminine than the other two who turned out completely massive, and others grew to be the same size as the others of their breed. As long as she's doing well, as you said, no worries. But there's not way to tell if...