In the future try and refrain from using laxatives. Constipation is usually attributed to lack of fiber and/or water in the diet. It's not good for adults to use, so probably not to good to start using with a child other a rare occasion. Eating diary to often can make that worse. For instance, my child is almost 6 and has never been constipated since we eat lots of fruit & veggies and always have water with us. Bloating is a know side effect for Miralax.
One thing you may find helpful is to gently message her abdominal area1 - 3 times a day in a clock wise motion. The bowels move in this direction. So if there is gas & bowel that needs some help moving, this is a great way to assist it. Plus it's relaxing, and can be an additional bonding time for you two. As a previews post mentioned Probiotics daily are wonder for the digestive system.
Sorry to write so much. I just enjoy sharing helpful info w/ other moms. Knowledge is power. Us moms as much knowledge and empowerment as we can get.
FYI: Sometimes what people think is the stomach flu can often be a sensitivity or intolerance to gluten (no, it doesn't necessarily mean Celiac Disease). Gluten is a complex protein found in wheat (white flour), barley rye, and some oats. It causes over 300 conditions (bloating & fullness is a minor one). http://www.glutenfreeworks.com/symptomology.php. My daughter and I have gone off gluten. It's a great thing. I've been in poor health for over 5 yrs. I recommend checking out that site. Over 85% of Americans have a disposition to be at least sensitive to gluten. If one has even 3 or 4 of the symptoms lists, one should consider getting off gluten. Many Americans go their whole life's with multiple health issues, not knowing that gluten is an underlying issue. It damages the small intestines and prevents proper absorption of many nutrients. Which, in turn, may lead to minor or major health consequences. The real sad issue is that the majority of MD's are minimally educated about nutritional issues, especially in regards to Gluten. So they truly don't know to check for it at all, or only check for Celiac Disease w/ a blood test or more invasive testing.
Going off of Gluten is good for anyone. It will save you money, by not buying so many processed foods (many which have wheat added, even when it's not necessary). And there are several bonus reasons, in my opinion. 1) after you eat you won't have the miserably full feeling 2) your overall health and well being will start to improve in probably a short time 3) without trying hard, one may easily lose weight (I lost over 60 with 7 months & still losing)