Okay, I'm assuming you watched the movie, so you'd know the context of the sub rel scene. She's searching for the location of the emergence. You'd think that in this scene she'd be running at MFTL+ speeds, then why the hell is she moving at only sub rel, which is, as stated by others, thousands of times slower by comparison. She knows the urgency, she knows what's at stake, so why would she move that slow if she could move at MFTL+ speeds. If it's shown she's consistent with Captain Marvel's flight speed in another movie, fine, fair, the feat can be used, but as of right now, we have one major on screen feat for her speed and its no where near that level.