Some bunnies’ urine can be an orangy-red color, especially if it’s not absorbed by the litter right away, say on a floor or plastic surface. It just happens once in a while, and is considered normal. If it is blood, then you want to watch for it to happen again and examine her again to see if it stops and a cut or scab becomes visible. Or if it is from her urine and clearly blood. In which case, take her to the vet to be checked. If it doesn’t continue, and she acts fine, and there is no scabbing or other evidence of injury, it could be the red urine I mentioned.
Be sure to check her paws, claws and teeth if you can. If it dropped from a broken nail, for example, that could cause a blood spot also.
I just saw that you posted the same question in Diet & Care, and received a lot of answers there. This would be considered a double post, so I’m going to lock this thread and refer you and others to reply only to that thread from now on. Please let us know how she is in that post. Thanks.