I think she does look like a young adult and could well be a 30 year old woman. I would say the appearance of characters' age can also be influenced by the surrounding cast of characters, as it sets the style for what certain ages look like. Like if a teenager has even bigger eyes and rounder features, then the first character will look older by comparison. As for face same syndrome, what can help is: - Drawing, even caricaturing, from a large variety of faces--old, young, long faces, wide faces, round, chiseled, and so on. I recommend trying out exaggeration, even just for a bit if it's not your ultimate goal, just so you can get a feel for how much you can push a character's features into stylization and step out of your comfort zone. And you can always reel it back towards realism/semi-realism afterwards. There is a course on caricature, and this lesson I think is especially worth checking out: https://www.proko.com/s/6Yt6 - Paying attention to proportion. Usually with drawing guides, like the Loomis model, you'll have a set of perfect proportions, which are really just the average of a human face. In reality most people deviate from those measurements, which gives us a unique and specific likeness. Practicing observing and drawing how proportions change from face to face can really help, and this video goes more in-depth: https://www.proko.com/s/xU4i - Practicing different features. Another study that can help is focusing on the variety of features at one time, like drawing 20 different eye shapes or 20 different noses from photos. This can help you focus on how features change from person to person and bring in more variety into your own style. It can also be worth checking out how other artists stylize features, as each artist chooses to approach and highlight areas differently. Hope this helps!