I have the same problem as your students!
I'm finding that I just need to remind myself to really SEE the details in life, rather than the whole picture. I'm generally good at this with nature. In that, I can imagine things in nature because I have memories of studying them.
Where strangely, faces and body shapes are not the same. It's like in my imagination my proportions get confused... So maybe features that are more noticeable in my subconscious end up being larger than life. I guess that could work in my favor for cartoons though.
Anywho! Thanks again for sharing your works and processes. I hope your student returns too!