Hi
You have not mentioned the frequency of her stools in a day. 
If the frequency is more than normal, it might be a dysentery- bacterial.
In such cases, kids will have 
fever, loose stools, blood in stools, pain abdomen, pain while passing stools. Treatment will be a good course of antibiotics.
The other possibility is 
anal fissure. This happens due to long standing 
constipation. When hard stools pass through the 
anal canal, they cause abrasions in the mucosa- which is called a fissure and is accompanied by a skin tag which is seen outside. It is a very painful condition. 
It has to be treated with stools softeners, local gels for about 3 weeks. Dietary modification with lot of fibers and fluids should be done.
So its better that you have her seen by a 
Pediatrician and get her treated accordingly.
Hope my answer helps you.
Wish your daughter good health.