She continues on, her strokes more desperate for air after getting to the wrong way. After reaching another way forward, she noticed all too late that the path back was being blocked off, leaving her stuck in the little space she found herself into.
As the lack of air seems too unbearable to handle, Sparkle think this might be it...until she realized a trapdoor right above her. She bangs on it desperately as this is the only chance she had.