huh interesting

Are her blood vessels partially visible from the surface somehow, perhaps?

Or special skin that can change color

Or skin that receive and deflect light differently

She a alien, there may other way even

Her eyebrows are the same color as those lines, which means that there could be hairs under her skin that occasionally turn up in a linear pattern across her body. It could be similar to how a horse shoos away flies from its butt using its tail.

Or she's a latent laser cannon that constantly struggles to keep its own enormously destructive power under control.

Her eyes are red, so the lines could be light receptors that regularly scan her surroundings from all over her body, giving her to some extend perfect 360 degree vision.