She likely has an ear infection, or a parasite called e. cuniculi is affecting her nervous system. Both conditions are very serious and can be fatal. Especially with her displaying a lack of appetite, you need to get her to a vet
immediately. It is an emergency if a rabbit hasn't eaten for more than 12 hours, combined with the fact that she needs to also get on meds for the head tilt.
The vet will need to check her ears for infection, but even then it can be hidden. E. cuniculi takes a blood test to verify if your rabbit may have it, but many times vets will just go ahead and treat for both conditions because it can be difficult sometimes to tell which one is causing the head tilt, and best to cover both possibilities. The meds needed are fenbendazole(antiparasitic), metacam(necessary to reduce inflammation), and an antibiotic. Many times baytril is the initial one tried but may not be effective and a different antibiotic like zithromax or
injectable pen g may be needed. These treatments need to be started immediately to reduce chances of the condition worsening and permanent damage occurring.
http://www.medirabbit.com/EN/Neurology/Otit/otitis.htm
http://www.gwexotics.com/wccms-resources/a/5/0/e/77554b90-a660-11e0-a685-0050568626ea.pdf
You also need to start syringe feeding if your rabbit isn't eating or isn't eating enough, otherwise your bun will starve. You can get a syringe feeding mix from your vet. Until then though, you can soften some pellets with warm water and try feeding that, or you can try hand feeding. You also need to ensure your bun is drinking or she will get dehydrated. If she won't drink you need to syringe water to her. Just be careful when syringing food and water, to do it slowly and carefully, in small amounts allowing your bun time to swallow, so your bun doesn't aspirate.
http://mohrs.org/index.php?id=palliative-care
http://www.specialbunny.org/head-tilt-ec/
You need to see a good rabbit savvy vet if at all possible.
http://rabbit.org/vet-listings/
http://www.rabbitsonline.net/forumdisplay.php?f=21