User blog comment:IamJakuhoRaikoben/Chapter 418: Challenger, Review./@comment-25111584-20150202144931/@comment-9595671-20150202151325

Agreed, being able to sense magic is a huge hint.

Plus I'm pretty sure Lucy still have to pay rent, so she's had to improve a lot. Otherwise she wouldn't be able to complete the big jobs to help her pay it, without Fairy Tail I doubt her journalist job alone pays the bills.