no no on the karo syrup: unless you dont mind giving your kid pure chemical sugar. i konw some people swear by it, but i would rather do the healthier choice.
prune juice is a good one.
but the key with constipation is to avoid processed foods/cheese/white bread misc and add more fiber to her diet. with more fiber, make sure she gets more water. fiber isnt digested, but it absorbs water; the more fiber/water in the stool the softer it is. one CAN go too far...
milled flax seed is a very easy addition to diet to add fiber. you should be able to find it in any grocery store. just sprinkle a teaspoon or so on pretty much anything... cereal, sandwiches, yogurt is a very good one, pretty much anything. its tasteless, though it might add a little texture. again, paired with water, this could be a great, easy solution.
but long term, concentrate on making sure you get lots of fruits and veggies and less meats and misc. i highly recommend choosing bread that has WHOLE grain/wheat as the first ingredient, and high fructose corn syrup is NOT listed (or down the list past the first 3-5 ingredients.) yes, it is more expensive, but i found that when i eat whole grain bread, i dont feel so stinking starving as when i ate white bread. man, that gave me a stomach ache for more food because basically, its sugar bread. its crazy.
anyway, ive probably drowned you with enough info. i guarantee adding fruits should help, and adding milled flax to things should too. less juice and more water (though, again, prune juice is good).
prunes are better :P the fruit. you know ?
good luck