Chickens, like any other creature, are individuals; some will become pets and some never will. And, some will change their opinion of you as they get older.
My first brooded chicks acted as if I was gong to tear off their heads every time I reached into the brooder. As adults, they run toward me for treats, and when convinced another hen might take the treat, will even hop onto my lap. It may be because they saw my grand dame hen getting all the grapes, and they wanted some, too. When I didn't harm her, it may have colored their opinion of me as non-threatening. Your friendly girl may have the same effect on the flock.
The hens that were raised by their own Iowa Blue mother still act as if I am planning to kill them. They will run up for treats, snatch them away as quickly as possible and eat at a distance. Attempts to physically return them to their coop means lots of running around for all of us, and plenty of noisy exchanges.
I've had my best success with handling babies daily; I often put them on my lap and loosely wrap the front of my sweater around them to help calm them and make them feel protected. This approach is working with my 4-week-old chicks as they are making "field trips" out of their brooder. One girl actually wants to stay on my lap rather than run around with her siblings. She may need a little push "out of the nest," so to speak.
I think careful observation will tell you if the chicks' sounds are happy or not. Soft, little sounds usually mean everything's okay while sharp, shrill sounds mean something's a problem.
Be patient because you are as new to them as they are new to you. Keep feeding them and working to keep them healthy, and I bet some friendships will develop for you.
Welcome to the group, and happy chicken keeping!