First of all, CRATE REST! I can't stress that enough. It is the number one most important thing you can do right now. The more your baby moves, the more painful her back will be. Your vet is right that if she keeps moving it will get worse and she most likely will need surgery. YOU CAN AVOID THIS! Is she in pain right now? Did the vet prescribe any medications such as a steroid or non steroidal anti inflammatory? The ruptured disc is probably causing a lot of pain and swelling around her spinal cord, and the sooner she is out of pain, the sooner she will start to heal. Has she lost any neuro functions at all?
Now, I'll let you know my Layla had a ruptured disc as well, and she is now paralyzed for the rest of her life. She's still a happy little girl in a cart, but she needs to have her bladder expressed and she can't walk or wag her tail anymore. We didn't know anything about her condition (she has been diagnosed with IVDD, a degenerative disc disease) and as soon as we saw symptoms, we didn't know the importance of crate rest, and it didn't take long for her to aggravate the rupture enough that she did severe damage to her spinal cord.
Check out this Yahoo group for more information and a whole community of people who have gone through this with their pets:
Dodgerslist : Support & Education for Disc Disease
And their website:
Dodgerslist Home Page
It is very very important for the rest of her life to keep her from jumping, running up and down stairs, or any rough play that might hurt her back further.