User blog comment:Miskos3/Fairy Tail Chapter 374: Revolution, Review/@comment-24467372-20140307123719/@comment-1359322-20140307150342

Lets see, the end result of that choice. Lucy and Lisanna would just get absorb by Franmalth instead.

Franmalth already absorb 2 of Lucy's spirit, just from that Lucy is unable to use her spirits to avoid making Franmalth stronger. Franmalth was able to fight equally against Natsu, Lisanna clearly wouldn't be useful against oddball.