K-Elf:
So sorry for you and your baby.
I have unfortunately been through this twice.
When the little guy pictured above was 12, he blew out a disc in his neck going down the stairs. We only allowed him to go down the 4 stairs on the front porch, otherwise he was carried, but that was enough to do it. NO STAIRS!!
He was totally paralyzed. In that situation you have to do surgery right away (I found out later) but the vet put him on IV and he stayed at the animal hospital for 4 days. He was released, but he was no better. He layed on a little pillow for a week until we had a follow up appointment with a surgeon. He had deep nerve reflexes, still, so she said she could try to operate. An appointment was booked. Well, Schnitzel HATES the veterinarian with a passion. Right after this visit he started to show improvement. He was able to get up on his back legs a little. I brought him into the surgeon again and when he was on her office floor, he hoisted himself up on his rear legs and frantically pushed his way to the door! She said to delay surgery. When I got him home after the appointment, he got up on all 4 legs and walked over to his water bowl for a drink. He looked at me like "Whaaaaaat?"
He made a pretty complete recovery, but I think he was very lucky.
The second time was when he was 14 and he got out of bed wrong.
This time he totally lost his back legs and did have surgery. He has recovered pretty much and can walk but not run.
He's 17 + now and still a character and fully ambulatory, though he does sort of sidewind around.
Our beagle hsa hurt his back much like yours twice too. He recovered fully through complete CAGE REST and antinflammatories.
It is really, really, really important to keep Isabella quiet and confined to a small place where she can't walk much. She sounds like she's getting better on her own, but you need to restrict her or she could undo her healing.
GOOD LUCK!!! We are all pulling for you!