Miralax is nothing to be nonchalant about. This a medicine that contains chemicals going into such a little ones body. I experienced this with my daughter and I never used any medicine.
I can tell you three things.
1)Make sure she drinks more water, especially when it is warm or hot outside.
2) Diet induced, evaulate her diet.
3)Natural methods can work.
My daughter at that age went through the same thing. The thing with Miralax is that it does not solve the problem and people tend to use it when one is having problems like these, but are they really looking into the cause or the root of the problem?
I can tell you it took me about a month to realize that my daughter needed more water because of the weather, less milk, yogurt and bread and we use organic apple juice to help her go. We let her take her time to push. The apple juice helped to her, but it stopped when I looked at her diet and water intake and as soon as I figured it out, she stopped. Miralax does not do that for you. I am glad you are looking into natural methods first!
Also, a doctor if going to tell you to go home and use Miralax or prescribe you something because they are in the business of using drugs. Many doctors no longer look into diet and nutrition or other simple methods because there is no money in that for the health industry and the second reason is that many people go to the doctor to get something, not for advice.