Depends on when you wean the kits, and it really depends on her condition. I have does that look marvelous 3 days after weaning the litter, and I have does that never quite "snap back" to show condition. (And I have one doe that never loses condition, even when nursing a liter! I could take her off the litter, put her on the table, and she would still place... BUT I wouldn't do that!)
If you wean at 6 weeks, evaluate her and check weight, fur, over-all condition. Evaluate her again a week later. If entries have to be in by then, you base your decision on how she looks that day. Each rabbit is different. Only you know how she looks and how she would handle it.