aww lisa so sorry to hear this and the pain you are going through
I lost a rabbit when I was about 7 as it had paralysis too, I was devastated at the time but my parents bought me a tiny baby rabbit even though I said I didn't want one but I did love it.
Losing a pet is really tough but you have to remember that their loves are shorted than ours it's just the way it is, as long as you give them the best of care when they are with you and allow them a dignified and pain free death you are doing your bit.
I used to work in a vets and have seen a few animals out to sleep and also held my 15 year old dog when he was put down. It is not distressing at all very calm and peaceful they just drift off to sleep.
You have done your best for her you gave her a fighting chance x