Bleeding - Cumberland,MD

If it's bright red, it's probably an anal fissure - a tiny little tear in the dry skin down there. If the blood were coming from inside, it would likely be dark.

Try putting a bit of vaseline or lanolin around her anus - sorry about the analogy, but sort of like you would with chapstick for a split lip. Same problem, different end. Moisturizing will help her be more comfortable, and help it heal faster.

And as Jo said, hard stools are a culprit, too.

Could be constipation, something she ate that's irritating her, a small tear in the rectal area (often caused by a rash or by really pushing out a hard BM. 99% of the time, it's nothing. Increase her fluids (water) and watch foods that bind her up.

Was it a hard stool? My youngest had very hard stools, made potty training delightful, and every now and then it tore the skin so you got a little bleeding.

If it only lasts a few minutes that is probably what happened.

It could be a milk allergy-my son had this and thats what it was. He outgrew it though.
Also could be from straining....are her BMs hard? Thats how you know.