T&P with you and Heidi. I hate how acute and scary spinal problems can be. If you are still in Texas, you might ask for referral to A&M. They have a package deal right now on backs and it includes all the imaging, surgery and aftercare Heidi might need into one neat little sum (and it's a lot cheaper than it used to be). It's too bad she's already had the steroids since she could have qualified for the study that they are doing right now, but those dogs have to have not been treated IIRC.

OU and LSU are also good choices if they are closer to you as they probably have the same capabilities.

Remember to ask your vet lots of questions - that's what we are there for - don't be afraid of annoying them, it's your right to know everything that's happening.