Ballard is a cutie. But wasn't she really only in 2 episodes?
No, she was in one episode, "Ashes to Ashes." She was retconned as someone who'd been part of the crew years earlier, but she'd never been seen before. Maybe you're thinking of Jetal from "Latent Image," who died under similar circumstances (Memory Alpha even speculates that Ballard was originally meant to be Jetal).