@lpetiti Like @willicreate says above, it is natural for your first attempts to be a bit still as you begin to explore, but I think you are doing yourself a disservice by jumping in to drawing your ideas rather than sketching them out. What I mean is your lines are rigid and controlled, rather than quick and loose, limiting your ability to explore and develop your ideas to a greater extent.
When you sit down to work on this character, it might serve you to look at and practice some character design poses on Pinterest or Google to learn how to "unstiffen" you drawings. Search "child character design" and practice with some of the drawings that come up.
When you are ready, take a minute to think about what your character will be doing in the story, and sketch out those poses (her whole body) as fast and loose as you can. Don't get caught up in adding too many details. Just practice drawing quickly, trying to capture her personality, which will be more than a missing tooth and a smile. Slowly you might find traits that begin to repeat in the sketches. And think beyond the words in the story. You are developing a personality that should have traits beyond those just shown in the text. What makes her tick, why is she sad (other than the obvious), why does she plant flowers, where is she from, what might have influenced her the past. That might be getting a bit deep for a kids book, but we should be creating characters that kids can relate to outside of the main story.
I look forward to see what you come up with.