User blog comment:Miskos3/Fairy Tail Chapter 374: Revolution, Review/@comment-24551285-20140307124205/@comment-7418318-20140307162438

What makes you think Franmalth can just snip his finger and the spirit is instantly absorbed?

If I had to make a guess I'd say that Franmalth absorbes his victims by first linking to them (like he did with Natsu in their first encounter) and then sucks them in.

If I'm correct in this, letting Natsu fight on his own is the worst thing Lucy could do. As the previous encounter showed, just letting his guard down once is enough for Natsu to be linked and unless someone's there to disrupt the process, it's over for him.