It honestly looks like a diaper onesie combo. Imagine how when it gets wet it's going to sag in the back than it already does because of so much fabric bunched up there. Totally looks like she's got a full diaper on under it
A DIY 10 minute tunic or dress. Take one wide and long scarf and cut slit in center, sew together at sides to middle, then with elastic bobbin sew at waist. Hey, if you used a belt you wouldn't even have to do the elastic waist part!