Re: Worried about weight gain
I think the questions you should ask yourself are "Is my daughter healthy? Is she happy? Meeting milestones?" If you feel the answer to all 3 is "yes," then IMHO where she is on the charts doesn't really matter. You don't need to be huge to be healthy- right now your doc is a bit worried but in a few years she'll probably be complimenting you on having such a slender child, and ask you what you're feeding her that's saving her from the epidemic of childhood obesity.
I would not take the Pediasure route- why pay for Pediasure when you have a better option that's free? Breastmilk, particularly in moms who have been lactating for >1 year, is one of the most calorie-dense foods you can feed your child. (I'd post a link to back up that assertion, but I'm on someone else's computer and I don't have my bookmarks file.)
That doesn't mean there's nothing you can do if you're concerned about your child's weight: there are plenty of high-calorie solids that you can offer, like avocado, cheese, meat, whole-milk yogurt, beans- and hey, why not add some olive oil to her lower-cal solids?
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"