at her age it is most likely an inner ear infection ….
she needs different antibiotics from the vet
and an anti-inflammatory for a few weeks to help prevent permanent damage
When antibiotics are helping, she will need to be on them for at least 6 weeks - rats often need to be on them for several months in order to get rid of the infection
please see:
http://ratguide.com/health/auricle_ear/otitis_media_otitis_interna_labyrinthitis.php
Please make sure she is staying hydrated and getting enough to eat as that may be hard for her
you can offer soft foods like:
her blocks ground up and soaked in cool water to make mush
organic soy infant formula thickened with baby cereal (Walmart online sells the formula if none is available in your grocery store infant section)
baby food
cooked sweet potato, cooked real oatmeal etc
and a water dish that can not be upset would be a good idea