Lucy (red (sword) dragon slayer)

Lucy has been making trouble for fairy tail because of her weakness. She founds out about the two different kinds of magic. The light and the dark. A voice tells her that if she chose the light, she would be strong but can hesitate to do something if a nakama is hurt. But on the other side, if she choose the the dark, she would be strong and she would be a dragon slayer. She wouldn't hesitate over something.
What will she choose??