Biting and strange behavior

[Toria]

If you saw my post about EVE-A my roborovski got caught by the cat so my attention last week was mostly on her. Just making sure she was with us still and getting her out twice a day for medicine.

However her little sister M-O was sorta shoved into the top part of the cage and didn't receive as much attention as she usually does. (she much tamer than EVE-A so she comes out alot more than her sister to sit with me)
Anyway I noticed towards the end of the week when i started to show her some more attention she had started bitting which she NEVER did before unless you held her how she doesn't like it. She also wasn't playing, just sitting in the corner staring. And i don't think she's eating as much.

I thought she was lonely so i re-introduced her with her sister on thursday (a week after the cat)
I've had to re-introduce them before when EVE-A hurt M-O and they went back together brilliantly.
However now M-O is attacking EVE-A. And EVE-A is still healing so i have separated their cage in half so they can still sniff each other but can't hurt each other as i don't want anymore injuries for EVE-A.

But its out of character for M-O and when their both in the play pen M-O doesn't play she just sits and stares at EVE-A who is running around and playing and goes for her when she gets too close. I'm worried about my baby M-O

Any advice?