If by Lucy, you mean the remains of the earliest Australopithecus ever found, then most of what we know about what she ate is based on analyzing fossilized teeth. Evidence points to a variety of food sources for our very early ancestors. Some of the items include fruits, nuts, grasses, seeds, and even other animals. Early species would have often tried to eat anything they could find most of the time that would consist of plant life, but when able our ancestors were willing and able to kill and eat meat as well.
Many animals are specific eaters, carnivores, herbivores, scavengers and hunters are classifications for what various animals ate. Our line was all four: we ate plants and animals, and we also hunted and scavenged for food. Lucy would be no exception, she no doubt ate anything she could get her hands on to stay alive.
If you meant some other Lucy resubmit with more detail.
