Pretty good, but I see some anatomy flaws. Where the hip meets the thigh there should be only one fold. Using two folds makes her look like she has a bunch of fat right there, and judging by the rest of her body, she shouldn't! Second, the sole of her front foot should be completely flat against the wall/whatever she's resting it against. Her thigh curves a bit too much toward the knee and, like I said, the rest of her body is too thin to look that chunky. The fold between her calf and thigh should also be more straight. In this pose, her back leg would be locked, meaning not so much of a curve at her knee area. It would be pretty straight with it actually curving toward the wall at the calf. I feel she's a little too skiny in the hips. The curve of her lower back toward her butt is too vertical - meaning too thin. Even if this is stylized, she would be more attractive with more lower back/hip. Her arm is very skinny, especially in comparison to the legs. The legs would be nicer a bit thiner, the arm would be nicer a bit thicker, especially around the elbow. The shoulder also attaches too high. It makes her upper torso much too long. Her chin also looks really low. Even with her face in that position, there would be a nearly straight line from the end of the jawbone (meaning slightly in toward the neck from the tip of the chin) to her neck. The face looks pretty good, but try doing some shading with the hat over her eyes to make it more dramatic. The upper lip should protrude more than the lower. They are currently on the same plane. Also, in the pictures I've seen of Carmen Sandiego, her hair is bigger and wavier, and her hat is a different style. So really, there isn't anything that distinguishes this picture as Carmen. She just looks like a girl in a trenchcoat and a fedora. Maybe put the belt on her too, that might make it more recognizable.
I would like to do an overdraw (meaning drawing over your picture to show you what I mean in my critiques). Is that okay?
I wouldn't usually be so nitpicky, but since this is a tattoo design, I think it should be flawless!