Sarah stopped at the realization of decreased mass. She felt lighter, steadily lighter, as she stood there watching her travelling 'companions' advance ahead of her. She slowly tilted her head, which had been bowed under her exhaustion, to peer up at the ever enlarging moon once again. She mouthed something strange to herself, and lifted her hands up high. She coughed, ash sputtering from her lips due to her having fallen a few times in the long hours of their trekking. She licked her lips, dryly, and sucked in a deep breath.
Then she crouched down low. She was lighter, and could feel it. It was unnatural, that it was, but she could make use of it. Starting low, in this crouched position, the girl began to spin; steadily rising up to her full height, the girl seemed to dance atop the shifting ash beneath her feet. She regained solid footing by virtue of ever-increasing movement. Her body started sluggish, but then began to move more fluidly. She was a writhing, gyrating, figure- and she was soon moving quite fast indeed.
Then she broke her twirling routine and took off at an immediate sprint back towards the tower [and thus those she appeared with] and leapt monstrously high into the air- sailing upwards, twisting her body to look up at the moon as she rose and spread her arms as if flying, then kept twisting until she glided forward as if carried like a leaf on the wind, slowly descending back down to the ground. This was...considerably faster than walking, to say the least.
Upon nearing the ground the girl would twist and plant her hands on the ground, carrying her momentum and swinging herself down to plant her feet and throw herself further and higher into the air at a much faster rate. Every time she rose into the air she would twist up to the moon and outstretch her arms as if frantically reaching for it, but then twist back to the tower in the distance and throw herself further forward towards it.
After two more jumps, she'd roll onto the ground and drop to her hands and knees, before sluggishly rising up and standing there weakly in a daze, her body heavier than even before unless something rather drastic occurred during this transit time.