Lucy's not lucy?

Lisanna's back and ever since poor Lucy's been ignored for 3 months with the exception of a few people. On her 18th birthday lucy goes to the guild praying to Marvis that everyone would remember....but they didn't except the few who did noticed she exsists. Natsu finally talked to lucy but only to tell her she's off the team. Then she accused of something she didn't do causing Natsu to call her names and tells her she's just Lisanna's replacement. Saying that awaking something within Lucy. What does this have to do with Master Mavis and Zeref?