(Last of my autism I promise)
Sparkletors pic of Em:

Direct trace:

This is no edit or changes to this trace, I drew those lines as close as physically possible:
COULD I SELL THIS?
-Yes.
Why?
-Because it falls under portraiture and references. Would it be weird? Oh extremely, but sometimes people have very distinct faces (like the soyjak memes) that make them extremely memorable so people do it.
Would I sell it?
-fuck no, she isn't distinct enough to be memorable and it looks like I fucked it up due to her disabilities.
Now, an edit a client may ask, usually wants a very flattering version, sometimes they even ask for piercings or tats they don't have to be included. In a commission of said person, it would look like this:

Many sketch styled portraits are erasing the ugly natural imperfections and making them into... well, a character. Like so^
You do this by exaggerating desirable features and shrinking ugly ones. So Emily's weird tumor nose would be shrunk down by about 10 to 20%, mouth shortened with natural curves of the lips more exaggerated, rounding out and maybe even lengthening chin to balance her proportions, short stubby lashes would be lengthened to a semi unrealistic degree (fully unrealistic without glue ons) more volumization and shaping of the hair, erasing unneeded details like certain lines on the face, etc etc. It barely looks like her but you could look at the two and go "yeah they look related".
WHAT SHOULD I NOT TRACE?
-other peoples' drawings. Photos are an entirely different medium with different rules, I also took photography and know this because of it.
CAN I TRACE ANOTHER DRAWING IF I MAKE CHANGES?
-you would need to make the changes so vast they it no longer counts as the same image, and even still it's expected that you credit the name of the artist as well as the piece by writing it down somewhere in the summary or title.
WHAT COUNTS AS "DIFFERENT ENOUGH"?
This is tricky, basically the best way you can garuntee it's fine is to have a stranger compare the two. If they look too similar and they can tell? Keep changing it if you aren't sure. Usually if you're copying a scene, you want the faces, outfits and armor, as well as hair/makeup/possibly skin complexion, as well as adjust the positioning of the subjects. If the painting or sketch has everyone holding their weapon high, add variety, some going for a swing, others stabbing. If they're raised in cheer, maybe have them clinked together in clusters or one big group. Color and values play a big role as well, think of all the different last supper paintings that look extremely different despite same people, positioning, and seating?
The clothes, texture, lighting, food on the table, facial expressions, they all play extremely large parts.