S.W.
Does her formula have iron in it? If so, try it without the iron and see it if helps. You can always add a bit of Karo syrup in it to help with the bowel movements. What kinds of veggies/fruit does she eat? Bananas will constipate a child and that is why a pedi will recommend them for diahrrea relief.
Does she eat grapes, dried cranberries, raisins, cheerios, canned/frozen cooked carrots, or green beans etc?? I used to keep a baggie of raisins, cheerios and baby marshmallows with me for my toddler grandson and he loved it. When I watch my grandkids, no matter the age, first thing I do is give them a bowl of grape or raisins when they come in the door. My adult kids could not figure out why I do that. My comment- No worrying about a tummy ache or constipation! Much luck!