There are 2 separate ways of thinking that artists need to learn. She need BOTH. The two ways are 3d constructive thinking, and 2d shape thinking. Both are equally important. Here's a guide to learning both.
2D skills
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Dorian Iten Accuracy Exercises
Level 1: https://youtu.be/HMX3K3YMbd8
Level 2: https://youtu.be/ecJO1LnjXpA
Level 3: https://youtu.be/LPywXVsRKT0
Accuracy guide:https://dorianiten.gumroad.com/l/accuracy?layout=profile
Use code "DORIAN" to get it for free.
The above videos + the accuracy guide is the easiest way to develop her observational abilities. No pencils, no knitting needles, no measuring shit. Just train your eyes to be so accurate you can draw anything with no effort, perfectly. This takes years.
Try at least 30 minutes a day. She shouldn't be depressed if it comes out badly, she should just do a bit every day and try her best.
Ethan Becker Dragging Art over Reference: https://youtu.be/RXb-Y_kz2aU
The above link is the same thing, just applied to cartoons / animation industry.
These are very important, because observational skills give her the ability to duplicate her instructor's strokes. In other words, it's impossible to properly learn construction, gesture, anatomy, lighting, composition, color, if you cannot even emulate what the instructors are showing you. Observational skills are like reading skills for writers. Reading by itself cannot get you good writing skills, but it's a necessary foundation that you build your writing skills upon. Reading and writing is both important for the writer, and 2d + 3d skills are both important for the artist.
3d skills
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There are many ways. Hampton, Vilppu, Weston, Peter Han, Loomis, David Finch, etc. I recommend torrenting a course / downloading a book for her and getting her to follow it. Do one lesson a week. DO NOT RUSH. Repeat the homework over and over again, even if she think she's already good at it. She wants to practice the same lesson beyond the point of boredom. When she's done with a course, go back to the first lesson and repeat the course.
All form drawing courses pretty much teach the same things too. One is not necessarily better than the other. But some teachers might say things in a way that makes more sense to you, so it doesn't hurt to poke around and see which works best for her.
Some courses which might interest her:
Ron Lemen: https://www.youtube.com/@RonLemen/videos
Glenn Vilppu: https://www.bilibili.com/video/BV1Fr4y1q7nK?p=2
David Finch: https://davidfinchart.com/where-to-start-and-where-to-go-from-there-a-roadmap-to-professional-quality-art/
Don't do all 3 at the same time, just pick one and stick with it.
The above links mostly concentrate on figure drawing, which is probably the best way to improve her drawing skills. If she can draw human characters, she can draw anything! Ron Lemen's youtube is pretty much a complete, overly-detailed college course on figure drawing, so if you just do that, you'll go from knowing nothing to knowing how to paint a figure in full tones. I, however, love Vilppu much more. I think he's much more skilled than Ron Lemen, at least when it comes to imagination drawing. He can be difficult to get into, but the more you draw, the clearer his words become. All 3 courses are very good though, you can eventually get around to studying all of them.
Now for the David Finch roadmap, I think this is the best one to follow out of all 3, because of how concise and simple it is. Also, Finch gives you a direct transition from fundamentals into making the exact kind of art you'd like, whereas with Vilppu you're stuck with Renaissance drawing and the transition to anime or whatever is kinda difficult. When you get to the Bridgman step, remember that you don't have to use Bridgman, swap it out for any other anatomy book, I suggest . And make sure to use the Cognitive Drawing method instead of the more difficult, impractical method he outlines in the guide.
Other useful free online resources:
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drawabox.com is a great course that'll teach her draftsmanship, basic perspective, and construction
These two links are a collection of art resources, references, communities, channels, and video courses that cover every major subject:
https://hackmd.io/7k0XRnIQR6SValR77TDfZw?view
https://sites.google.com/site/ourwici/
Gesture drawing and quick-pose drawings are important too. Practicing this will preserve the energy in her drawings. quickposes.com
sketchdaily.net
characterdesigns.com
lovelifedrawing.com
posemy.art
line-of-action.com
Your kid did a good job. My only complaint would be that the words won't be legible unless you're right next to the person. Increase the contrast between the background and lettering, peach on white is too similar and it'll blend in from afar. This can be done by darkening the outline around the letters, and/or darkening both the interior and outline color of the letters.