Female rat who won’t except other female?

[jorats]

This usually happens with my males on occasion. What I like to do is remove the "aggressor" from the cage for some one on one for a few minutes with me. Then I put him back. Another thing you can do is also take Nibbles out and feed her some baby cereal or Ensure/Boost, you don't want a rat going too skinny.
Zoey is displaying territorial/alpha behaviour, for some reason she's decided to pick on poor Nibbles. I don't think it's enough to separate them but I would intervene and take one or the other out for some special cuddling. Taking out Nibbles could make it worse for her, so I recommend taking out Zoey.
When there's a territorial rat getting too bossy, we have to remember that not only the victim is stressed out but the bossy rat is as well or else he/she wouldn't be acting that way.
Also, sometimes a spay helps calm down a female as does neutering with males. I've seen it in some of my females but I wouldn't say it works 100% of the time. Yet, in my opinion, neutering works 99% of the time in calming the male.

 

[mamarat2]

I was all set to post a reply up here earlier and the spell checker just would not let me!!

So I wasn't sure if this is an intro you are working on with these rats or just something that is ongoing?

If its an intro I have found that with girls there is always one alpha girl in the pack that causes trouble for the newcomer. If this persists or even to begin with I try to get the new rat to bond with one of my more maternal girls, I do this because then when I try for full on intros the two rats that are already bonded (newcomer and maternal rat), the maternal type rat that is already a part of the group tends to put herself into the middle of the altercation between the two or it is even prevented in the way.

Of course one other thing I have noticed with girl intro's is once the "alpha" rat has fully gotten into it with the newcomer they usually get over it, unlike boys who drag it on forever. I seem to have bad luck with boy intros!