Oh my Gosh--that baby's grandma would flip over that photo!!! What a lovely dress she has--soooooo well-matched to a tea party type shot! My main issue with the photo is that the baby's head is too high, at the very edge of the frame--and that causes visual tension which is not desired in this instance. She needed to have more space above her head. I agree, it also does look a bit underexdposed. The lighting looks "flat", and I think you could easily LIGHTEN IT UP, a LOT, and make it feel very spring-like.
I know you JUST bought Lightroom, like a day ago, so you'll soon see how amazingly easy it is to edit shots made under low-contrast lighting like this.