That end declaration confuses me as well. However, it's hard to see this to be a sudden last chapter, especially due to the Dae and Rubel's talk, which would have been a very strange thing to leave there if the manga had been cut short.
Just moment before she told the other two to slay any organization men they found - so for her to say it's enough for her to be the only one to soil her hands is a bit questionable. Unless she was absolutely sure the other two would find nothing. But in that case she wouldn't have seemed kind of surprised to see Rimuto down there. Maybe there was a translation error and she was really talking about being the only one from that land to kill those monsters?