Re: 5x08 The Hungry Earth (Grading/Discussion) SPOILERS!!
Maybe because they really feel threatened by the humans now? They might also be a bit irrational.
In any case, I wouldn't take one Silurian's word for the whole truth. She's a warrior, and they often come off as paranoid/belligerent, at least our militaries do to some extent.
"Now and then we had a hope that if we lived and were good, God would permit us to be pirates." Mark Twain, Life on the Mississippi