Check her water. Are you getting from a different source? If she's drinking from a water bottle, check the nozzle. Make sure she can get the water out easily. If she's not getting enough water, she's not going to be eating. You may need to take it apart to check it out and fix it. (Thinking water valve stuck/dirty)
Check your feed. Is it a new bag? Old bag? Dusty? New brand? How does it smell? Sweet? Is it green, not gray? What's the mill date? (Thinking bad feed/change in feed)
Is she getting hay? (Thinking fur block) You can give her papaya, pineapple, pineapple juice, or Petromalt (for cat hairballs).
All those things might make a rabbit go off feed.
Do a external health check, including teeth, to check for any hidden problems.
Did you palpate her? All my does go off their feed the day before they kindle. If there is ANY chance she was with a buck (you tried to breed but though she missed), I'd put that box in there. It can't hurt.