It's a shadow, guys.

I screencapped a higher quality of this:
For the fan artists out there such as myself, it's easy to tell that this "stripe" is simply a shadow of the bump of her shoulder that is facing
away from the sun. The sunlight is coming from the bottom right of this shot, just as it does before it's about to set, making the lighting look a bit unusual.

Notice that her "stripe" in the first pic and her shadow in the next are exactly the same color.

Case closed lol.