Even though you knew it in your heart, you must have been glad to hear the vet say that she wasn't ready to be put down at all. Whew!
I don't know how short of a course the Prednisone is, but that may be a little challenging by making her need to empty her bladder more often. Thankfully, as soon as she stops it, it reverses itself, unless one of the other medications has the same diuretic-like effect.
8 weeks? Really? Yikes! You should buy the Miss Clairol now!
Then again, he's just estimating. Maybe it will be somewhere between 3 and 8 weeks?
It may be that Arwen's play, as a young and happy pup, has made the back worse to begin with, and it's not just her being a klutz?
Good luck! But, at least you know what you're dealing with, and have medication to back up your efforts.
I'd be tempted to dig out the Valerian - for Arwen, that is!
Please keep us posted on how she...and you...are doing!
Love All Life, Thank You For Posting! :)