I'm sorry, but I have to completely disagree with your vet on having to put your rabbit down. Many rabbits with severe head tilt, have recovered. It can sometimes be a long process with daily meds, and sometimes there can be some permanent damage, but the rabbit can still live a very good happy life. It's going to depend also, on how able you are to help nurse your bunny through this, as it can sometimes be quite a process, especially if she needs hand feeding every day. The rabbit could recover in a few days to weeks, or sometimes it can take longer.
First of all, I would suggest finding a better rabbit vet. Your rabbit should be on at least oral antibiotics as well as the anti inflammatory metacam. Some vets will give steroids if it is very severe, but this should be carefully weighed as steroids can lower the immune system, and with your rabbit not being on antibiotics(aside from the ear drops, which may not even be the best choice for use on a rabbit), it gives the chance of infection spreading. Then there is also needing to consider the parasite e. cuniculi as being the cause of the head tilt. Did your vet do a blood titer to check for this, or even mention the possibility? Basically any rabbit with head tilt needs to be on a rabbit safe antibiotic, the anti inflammatory metacam(if no kidney issues), and the antiparasitic fenbendazole. The antibiotic and antiparasitic will cover the possibility of an infection and e. cuniculi, and the anti inflammatory is needed to bring down the inflammation from both illnesses, as the inflammation greatly contributes to the symptoms of head tilt and rolling that you see. If the inflammation isn't reduced it leads to the greater possibility of permanent damage occurring.
There's a good chance she can recover if she is treated correctly and given the right medications. You do need to ensure that she is able to eat her food. You may have to make adjustments to where you place it and her water. If she seems to struggle eating, sometimes it's necessary to syringe feed a rabbit, until they are able to eat on their own again. You can get a syringe feeding mix called Oxbow Critical Care, from your vet usually. You will also need to syringe water if she isn't drinking well on her own, which needs to be done slowly and carefully so nothing gets aspirated. You'll want to keep her in a smaller area, and it's helpful to place some padding on each side of her, to help support her from rolling. Also picking her up may make her dizzy, which can cause a rabbit to panic, so if she reacts badly to picking up, it's best to limit doing it as much as possible. Here are a few links on head tilt as well as some rabbit vet listings.
I'm really sorry about your bun and hope she is feeling better soon.
http://rabbit.org/category/health/neurological-problems/
http://www.medirabbit.com/EN/Neurology/Otit/otitis.htm
http://www.medirabbit.com/EN/Neurology/cuniculi/pyrimethamine.htm
http://www.woodward-vets.co.uk/information/Encephalitozoon%20cuniculi.pdf
http://onthewonk.com/?p=1.Home&trk=menu:Home
http://www.rabbitsonline.net/f28/finding-vet-13366/
http://rabbit.org/vet-listings/
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