It seems to be fairly standard for them to get worse as they get better - it's all part of EC and she WILL get through it with support. Make sure she can't hurt herself, can get to food and water, and she is kept clean. Restricting where she can go will help until she has more control, and she may need access to a heat pad (eg snugglesafe microwaveable one) wrapped in towels or similar - but she needs to have the choice of whether to be on it or not.
Did you get any more anti-inflammatory for her? They usually only last 24 hours and she should be on it daily to prevent long term damage to the nervous system. If you haven't got any (eg metacam), I would ring or go back to the vet and ask for some as a matter of urgency. Keep up with the Panacur as well.
Several people on here have been through this. My rabbit started with it last Christmas. She improved in the first week or two, then got much, much worse for a week and then started to get better. At her worst, her head was doubled right back to her side and she wasn't able to stand or clean herself - which meant she also couldn't reach food or water, so she was syringe or spoon fed. I kept her in an indoor cage with deep hay so that she was comfortable, cleaner and could eat the hay. She is now back outside in the run with her partner.
She has had a couple of minor relapses during the year for which she has another month of panacur and almost permanent metacam - but she does have other issues as well. If you had seen her at her worst, it was really heartbreaking to watch and I considered PTS a few times. Looking back at posts on here helped, plus the fact that I was more distressed than she was and it was just a matter of more time and TLC to get through it.
I personally would not be considering PTS if she is still eating (with or without help) and weeing / pooing normally, and you are able to cope with the medication, etc. She needs lots of nursing and TLC at the moment. Ask your vet for advice if you are worried. You could still book in to Crab Lane vets for some expert advice and explain what has happened so far. They are THE rabbit specialist in Yorkshire. Your vet could also ring them for advice if they are not familiar with treating EC.