I also found this ....
Mucus is found naturally in the digestive tract, specifically in the intestines, to keep the lining of the colon moist and lubricated explains MayoClinic.com. It is possible for some mucus to be passed during a regular bowel movement as it moves down the lower intestines and colon. When this small amount of mucus appearance infrequently, it is not a reason to worry. Caregivers should still talk to a doctor about it when it occurs in their child..
Read more: http://www.livestrong.com/article/293030-mucus-in-a-toddlers-stools/#ixzz27o7DyJz0
Has she recently been sick, had a cold , and sometimes foods like milk can be a cause .