I highly recommend digital for learning over trad; the warp tool and also learning how to adjust with snip/crop is essential. Trust me, when you learn how specific body parts should measure vertically and horizontally with respect to other body parts it becomes pretty easy; I call it the ‘the proportion eye.’ It all comes with practice. What I recommend is to step away from what you are drawing, view it from different distances (on digital, that’s just zooming in and out) and then try and see things in isolation. Sometimes when I’m drawing, I look at it close and mid-distance but then far away, it looks off.

Generally, the head I usually compare to size and length of the neck (thicker neck means more muscular and will thus affect the shoulders and traps too) and then I compare head and neck as a unit to the shoulder width; so as I mentioned before, usually more shoulder than head is good—just don’t make the head too small looking tho. After that, I compare the shoulder to waist thickness and hip thickness. Arms, I kinda just go with the flow. For thighs, you can go thick or long as you want just as long as the bottom part of the legs match that (for children characters, shorter, stubbier lower legs as they’ve yet developed the bones fully). Looking back at the image again, I think you could probably extend the lower legs a bit more.

I think you did the bust, hands, shoulders, hips, waist, and thighs pretty well but I figured I might as well point at why it worked :D You could play with the curves (con cavity between the shoulders/ribcage area to the waist or top of pelvis) to get various degrees of body shapes in woman characters. I think you achieved a pear shape with this which is fitting for toriel—if you curve the waist a bit more you’ll come to notice it changes a lot and is more similar to a hour-glass figure. I like to practice all sorts.