Probably not the right place, as there are quite a few arrogant people on this forum (and indeed in physics in general). Check out /r/asksciencediscussion for a friendlier community.

You have a few things confused in terms of terminology, but it's no big deal. Let's work through a few thought experiments to help you understand. There's a way to manipulate the science to get what you want, but it's probably not in the way you expect or want. For a comic however, how hard the science is becomes irrelevant after a certain point.

So you're in a ship in space, and I'm moving past you very quickly. Since all reference frames are relative, you are also moving past me very quickly. Now if this relative difference in "speed" is large enough, if I were to look at a clock you are hypothetically holding, I would see that time is moving more slowly for you. Same if you were to look at my clock, again because frames of reference are relative.

So, just because I see time has slowed down for you, does that mean I'm all of a sudden not moving past you as fast? No of course not, I'm still moving past you at really great speeds and you are still moving past me at great speeds. So if Shift is really moving so fast as to see time slow down for other people and objects, she would still see them moving incredibly fast relative to her for the reasons I described above.

Now, if you actually want her to see things "slow down" in her environment, it comes down to a combination of things that changes her perception. This can be simplified to two things: the amount of information her senses take in, and how long it takes her brain to process it. So a simple example of this is when you have your adrenaline pumping, your senses sharpen and your brain begins to take in more information and processes it faster. So you are able to see the finer details of a ball moving directly towards your head, and you are able to think about what to do faster than you normally would. Because your brain has more data to sift through the memory of that moment of split second ago seems to have taken longer, even though the same amount of time had passed. Another easy example is imagine sitting in class day dreaming. Time goes by much faster in terms of your perception when you have no clear markers of it passing than if you were to watch the second-hand on a clock ticking away each second.

So your hero would need three things: Hyper senses to have as high a resolution of data for her environment as possible, Hyper brain capacity to interpret that data much faster than a normal human could, and the speed factor to be able to physically move fast enough to take advantage of the latter 2 abilities.