Obvious stuff like a fake shimmer or really dark lashes. Very plump lips. Careful penciling around the eyes, eyebrows or lips.
"Cover-up" -- Nobody has perfectly even skin on their faces. If you see a girl with perfectly even-toned skin, she usually has some sort of foundation/"base" on to diminish shine and hide uneven skin tone to give that silky smooth effect.
It's part of the "natural look" -- that look that gets guys to make a girl look more approachable, less "high-maintenance".
I hate make-up as a rule and yet a little mascara to make the blond lashes visible and a touch of "natural" gloss before a party or get together to make my pouty mouth "pop". The guys don't seem to mind and never complain, haha.
Look at her neck and if there are two different shades. Not to sound rude but if there skin looks too perfect then they probably have some on. By too perfect like literally not a single flawed mark. Also their face will look kind of powdery. If its extra bronze then probably.