Glad she was spayed! Bigger dogs are prone to hip dysplasia.. I had a Rottweiler mix for 10 and half years and she had mild hip dysplasia and she didn't need surgery, thankfully but we would have done if had she needed it. She actually never needed meds for it either, she lived out a good life without pain.

How old is Zoey now? Surgery may be the best thing if it's really bad, but there is also a possibility that she can tear her ACLs later in life. I would see what their vet thinks as it's a big surgery and not all dogs need it, usually meds can control it. Did they send her home with any joint supplements? Glucosamine is a really good one.