Have you gotten your pediatrician's input about the pediasure? My son would still be breastfeeding had he not weaned at 9 months so I had to supplement with formula until his first birtday and until he is 2, my pediatrician recommended that he be on whole milk. I have used pediasure, but ONLY as a treat. I do not believe it should be used the way you are using it. It should not replace meals and it should not be a substitute for milk. With that said, I would speak to your pediatrician about using the pediasure in place of milk.
As for the picky eating, I have one of those and I know how frustrating it is to find something for your baby to eat. I don't make separate meals for any of my children. They eat what we eat as a family...or they can go to sleep hungry. With my 22 month old son, he is picky. What he may gobble up today, he may turn his nose to tomorrow. It's really a hit or miss with him and I get so frustrated. Here are some suggestions that seem to work for me:
crackers with jelly, grilled cheese sandwich, macaroni and cheese, spaghettios, bread with apple butter or jelly, chopped apples, sliced bananas, french toast, pancakes, Cream of wheat, Oatmeal (unflavored,no sugar), small pieces of cheese or cheese sticks, yogurt, soup. Sometimes my baby just isn't hungry when it's our regular meal time so I'll try feeding him a little later. Another tip is to give her really small portions. It's easier to put more on her plate then to have her feel overwhelmed with heaping portions in front of her. I usually put about a teaspoon of whatever I serve on my baby's plate.