We did not have to make a trip to the vet today! Roo is doing much better: she's eating and drinking and not vomiting! She's kept everything down for 36 hours, now we're waiting to see when/if she'll have a bowel movement. Let me tell you, I never thought I would look forward to picking up dog poop.
Her balance is still off, and she falls over when she shakes her head or tries to chase a cat - but at least she's back to wanting to chase cats.
Thanks everyone for your good thoughts and wishes.