She was capable of crushing ships, but simply didn't kill everything for plot reasons. And I don't believe life drain is on a galactic scale. And to be honest I don't remember why she was running. I don't even remember her running. If she did it was likely an avatar trying to escape. And her she didn't seek to destroy all life. She was originally the mother of the Ones (god-like beings who were immortal, but capable of being killed by a special dagger), but wasn't immortal like the rest of her family. In order to become mortal, she bathed in a special fountain and did something else which corrupted her.