Hello, First before jumping to the vet. Go down to walmart, by a ripe avacado. Give her a small amount of that. Also get some pedialyte (No citrus fruit combos) pour a small amount into a cup and put a lot of water in there (so its very light in color). Give her a couple drops in a syringe to her. Do this 1 to 2 times a day for about 3 days. Also get some baby food (still no citrus fruits or high in sugar) Give her a small amount. You dont wona give to much or she can get the runs. This should clear it up in about 5 days, if shes still not doing better then she will need to see the vet. Plus try a warm bath (not to warm and not a lot of water) just enough for her it to be up to her legs. Dont wont to stress her. Check ears, mouth, nose, and eyes for pus. Also put the food bowl and water where she can get it. If she is sick she wont want to have to try and figure out how to get to it. Also I would seperate her from the rest of the rats, dont need any one else sick. Hope this helps and I hope she gets better keep us updated on how she is doing. If you have any other questions or need help please feel free to e-mail me.