Hiding in the shadows

Maybe not off-putting, but just a bit confusing. Even light skin and hair do not tend to be that striking in shadowy enough spaces. If it's dim enough that she stands out there's probably too much light anyway for a hiding space, and the MC won't choose for them to be there at all, so I'm assuming you're talking about near total darkness.

If the point being made is that she's exceptionally pale, perhaps it's something your MC would at first sight take note of and you might not need this part in the scene just as a way to work in the appearance of her hair and skin.

If the point is to cover her up for her to blend easily into corners, it looks like your MC might need to be covered up as well anyway. In darkness they'd both be mostly safe, but if the problem is that there's a risk of their ankles catching a sweeping beam of flashlight or something like that, both dark and fair skin would be noticed.

Human skin is shiny regardless of skin colour. It reflects the light. So a human trying to be stealthy will cover or coat their skin. They're not going to not bother because they're brown. Consider that black soldiers don't forget about their camos and war paint because they're brown. It's not how it works.

In reverse, if a white cyclist goes out at night, they don't forget about reflective clothing because they're pinky-pale.

This isn't to say that a naked black person and naked white person have an equal chance of being seen in darkness. It's that this is usually completely irrelevant, because neither of the naked people is in a safe position... and because people will usually be wearing clothing appropriate to the task. The way it gets emphasised in some fiction is really strange, because like I said, we'd think it odd if black soldiers ran around naked because they're brown. Their clothes are clearly better designed for staying hidden than their skin.

The most important thing about hiding in darkness is to break up your outline. A moving patch of black clothing is just as noticeable to an observant guard. You need to blur the shape of your body.

As Polenth said, skin colour doesn't really have much to do with it.