Im not sure if it was mentioned before that Lucy's mom, also a celestial mage, was connected to "The One" magic. Also her mom was gone the same year the dragons disappeared. Or if it has something to do with Lucy being the one to be sacrificed back when they fought against that particular guild where Gildarts had to fight the octopus guy and erza fought with the lady samurai mage. cant remember the details. there's definitely more than just luck in Lucy that made her able escape Algeria. something she's not even aware of.