Hmm, I've dealt with older hens pecking on the younger ones, just for pecking order. Maybe a roo would do? The hens usually sleep next to them and they aren't like mean to the hens unless you get a nice roo.
If it gets cold out there where you live, I recommend getting like 2 more, so she has some buddies to hang out with in the coop and keep her warm, and also learn her chicken ways.
Also it's good you joined!