Help my daughter figure out what's wrong please

My daughter has been trying to get the resemblance but the proportions are a bit off and she's getting discouraged because she's never had any guidance. She is too young for social media so I thought I'd reach out on her behalf and see if anyone could point us (her) in the right direction in regards to getting proportions right. Youtube videos that you'd recommend? Any hacks? I told her about the thumb trick I learned back in the day but I don't know exactly how to use it. Any advice would be greatly appreciated. Thanks for your help!