Sometimes, chickens develop hard growths or scabs on their beak if the beak has been injured. I know that when my birds get a injury on their beak (for example, when they fight with another bird through wire and the base of their beak rubs again the wire), it often develops into a lump or scab. One of my birds in particular got a small scratch on her beak that turned into a hard lump. It went away in a few weeks. Your bird is probably fine-- if she continues to rub the beak on something (wire fencing, etc), it may not go away for a while, but should eventually.