Here is the protocol I follow that works very well and I'm sure you can find the equivalent medications without a prescription. I apologize that the protocol refers to "he" rather than "she".
Chronic constipation is a common problem in children, especially boys. The protocol for treating this, while fairly simple, does require strict adherence to it for many weeks or months before the problem improves. Here it is and please let me know if you have questions:
First, all children with soiling have chronic constipation and have colons full of stool. This needs to be evacuated completely so buy a few Pediatric Fleet's Enemas and give him one now, one in the morning and then you can continue to use an enema if he goes more than 4 days without a stool.
Second, eliminate all dairy products from his diet for now as the calcium in dairy caused the colon to slow down and the calories from dairy products only spoil their appetite for other foods. Increase his intake of juices, especially apple juice, as this will help with keeping his stools soft along with the next step.
Start him on
Miralax, 2 teaspoons daily in juice, to help keep his stool loose or soft and moving.
Over time his colon will shrink back down and he will regain his control over his bowels in time, but you should expect this protocol to work only if he is willing to participate fully in it.
He should sit on the toilet after each meal for 5-10 minutes to help retrain his bowel to respond to the natural urge of needing to empty after meals.
It may take weeks or months to see improvement but if you stick with this protocol I've yet to see a child not get better eventually.