Not sure what you are feeding her...but I would suggest you really up the table scraps and high fat/protein foods. If she got pregnant back to back she has pry lost most of her reserves which means her body is eating itself.

I had a rat that I accidently let this happen to and she did the same thing (got really skinny, started to loose her hair, etc.) I gave her nothing but table scraps and perilite (to drink) for 2 weeks and she was able to pull through and went on to live a good ole long life.

Hope this helps,
Sean