Originally Posted by
Alty
It sounds like something tore her rectum, but without seeing your dog I wouldn't be able to say for sure. Also, I'm not a vet, so even if I saw your dog I couldn't give a diagnosis.
If she's eating and drinking, book an appointment with your vet tomorrow as soon as they open. Bleeding should be checked out. If she suddenly stop eating, is lethargic, or goes from being seemingly healthy to a complete turn around in the other direction, I would go to an emergency vet. But seeing as she doesn't seem to be sick other than a small amount of bleeding from her bum, you should be fine seeing the vet tomorrow.
But that's just an opinion. No one online can tell you if this is an emergency, or something that can wait. That's your call, you have the dog in front of you, you know the dog. If you feel she needs to go in right away, then that's what you should do.
Let us know how she's doing after her vet appointment tomorrow. :)