User blog comment:IamJakuhoRaikoben/Chapter 468: Memory of the Stars, Review./@comment-26389992-20160110033908/@comment-7418318-20160110093726

True, but on the other hand she probably didn't have much of a starting point to look for Layla or her possible descendants.

Not knowing where to start is quite a dampner for vengeance.

Thinking back to the island, I now wonder if Lucy's presence might have been the reason why Brandish let the team go in the first place. With her power she probably could have easily wiped them out and thus fulfilled the orders she had from Zeref, but she disobeyed those orders.

Despite seeming so loyal she did disobey her orders right there. If Lucy's appearance shook her up and brought all her traumatic past back to the fore of her mind, it would explain this odd behaviour (even Marin was surprised out of his mind about Brandish's choice, so I think it was out of the ordinary for her to act like that). With her thoughts being in turmoil she didn't immediately act on her suspicon about Lucy being Layla's child and by the time she made up her mind, Lucy was already gone from her grip, which would later prompt her to ignore the battleplan and go after Lucy instead.