Look up enrichment ideas for dogs, puzzle toys, or nosework games. These are designed to engage your dog's brain and help them feel fulfilled and satisfied, but in most cases are very easy to do in small spaces and with low physical exertion. You can also try teaching low-activity tricks (a nose or paw target, for example, or putting a toy in a box, walking backwards on command, shake, play dead, etc), basically pick anything that seems fun and low-pressure as a way to work her brain and build your bond. Offering chew toys she loves or part of her meals stuffed in a food toy like a Kong Classic or Toppl is also a wonderful calming, stress-relieving activity - you can freeze food toys to make it more challenging if she empties them super fast. Mental stimulation can't replace physical exercise long-term, but it can work really well to make surgery recovery more bearable for both of you.