J.B.
My nephew had this problem too. His pediatrician recomended 'miralax' it's available over the counter now and it is gentle enough for infants... it's a stool softener and it's safe to use for long periods of time. My nephew, now 5, used it from about 6mo to 4yr, now he just has to take it occasionally. It is a powder that you can mix in ceareal or whatever she eats/drinks well... it has no taste, I've tried it. Good luck, I hope this works!