Rat bites

Question
I have had my two female rats for a year now and have had no problems with them. So they are probably a little over a year old. They are unaltered. I got them from a pet store. Up until this point they have been very sweet and one of them even licks me. I let them out for about two hours a day to explore and spend time with me. Just recently one of them bit me. I noticed that she wasn't acting like herself. When I stuck my hand in the cage she shrunk away from me and was in general, not acting very friendly. I left her alone for a while and tried to pet her again. She bit me. For about three days now she has been acting the same way and I am sure that if I got too close she would bite me again. She is acting pretty normal around her cage mate, maybe only a little more agressive than usual. I haven't changed anything and I haven't noticed anything strange going on besides her behavior. She is just as active as usual and eating normally. Do you know why she may be acting this way and what I can do about it? And also, Nikita, the one that didn't bite me and the one that licks me has always been the more dominant one. Gypsy, the one that bit me, was always a bit more timid. Does that have anything to do with it?

Answer
That almost sounds like a rat who is uncomfortable, injured in some way or otherwise not feeling like herself. My first thought was pregnancy, however if she's only been with females, that isn't a viable option. Is a vet an option? I'd have her checked out for any underlying health issue, as that's usually the #1 reason for sudden personality change. If not.. well.. I'd try to just let her do her own thing and just keep an eye on her. I'm very sorry you got bitten - that hurts! Good luck.