Bring in another bantam?

I have three 6-week old pullets (barred rock, and 2 EEs) and a bantam brahma. The banty is frequently off on her own and seems to me like she's left out of the flock. She's super sweet & docile and just always seems to be left behind. I assume she's falling to the bottom of the pecking order (how do you tell?) but I'd love to bring another banty home to keep her company. That said, I assume there are no assurances that they would even hit it off & I think I've read that it's tough to bring bantams into established regular sized flocks? Is that true? Many thanks for any thoughts.