Reddit mentions of Cook's Illustrated Baking Book: Baking Demystified with 450 Foolproof Recipes from America's Most Trusted Food Magazine

An alarm clock to get her used to waking up at 2am? ;-)
I'm not a professional baker, but did work as one for several months 20 years ago. Enough to let me know that although I enjoyed baking, I didn't enjoy doing it as a profession. So these suggestions are from a home baker, not a pro.
I would suggest a cookbook or subscription to Cook's Illustrated or America's Test Kitchen.
I bought The New Best Recipe Cookbook ten years ago for myself and have gifted a copy to several friends since. It goes through not only a recipe, but what changing different ingredients will do to the final product. The chocolate chip cookie recipe was quite informative with illustrations showing not only what different sugars would do, but different fats, flours, and the effect of chilling the dough had on the final product.
There is also Baking Illustrated which is just about baking. It's probably going to be hard to find, but if you stumble across it, it's worth it. Some folks complain that it's just the baking chapters from the best recipe cookbook with a few extra recipes, but if your kid is really focused on baking, this may be a better fit for now and then the best recipe cookbook later when she feels like branching out into thing to go with the baked goods.
I do not own the Cooks Illustrated Baking Book but I have several of their other cookbooks and friends who have this one think highly of it. It's been described as a combination recipe book and class in baking. Like the New Best Recipe Cookbook, it includes not just recipes, but paragraphs about what is going on in the recipe and what changes to the recipe will do.
You may also want to look at getting a large vermin resistant container to store flour. I use a Vittles Vault pet food container to store my flour. It allows me to buy 25 lbs of flour for $8 instead of 5 lbs for $4 and not run out in the middle of a baking session.

I also recommend America's Test Kitchen Baking Book and Cook's Illustrated Baking Book. Cook's Illustrated is a magazine written by America's Test Kitchen so both books are similar. I have both and use them frequently. All of the recipes are tested and they explain why the recipe works. Everything I had made from all of the ATK books have been amazing.

I am a big fan of Cooks Illustrated/America's Test Kitchen. What I like the most is that a) the recipes do work as written and b) they go to the trouble of explaining the WHY, which is exactly what I need to know before I go off experimenting on my own. They have a number of baking-related books, but here's the main one