Sad Rat?

Does she have a cage mate? If she doesnt that most likey is the prob. She may also just be bored with her surroundings. Have you tried taking her into another room/ outside? Maybe get her some new toys? My Jay seems to get bored every once in a while too no matter how much attention he gets from me or his bro Bob...but he snaps out of it once I give him a few treats. Haha

Maybe she just has to get used to the cage. I know when I made my cage alot bigger, Jay didnt know what to do with all the room and he mostly stayed at the bottom of the cage. Bob had a ball climbing up and down it! Just give her some time, maybe thats the prob. Since getting your babies into the bigger cage, have the other two cage mates picked on her? Could be that the others are claiming certain areas of the cage and arnt allowing her to be where she wants to go? I know that Bob used to do that with Jay, but thats a dominance thing. Jay can go where ever he pleases now that hes older without a care from Bob, but when he was picked on he seemed really sad and needed alot of support and love from me and my BF.