Xavier Fitch: We decided to make it female so it would be more docile and controllable.
Preston Lennox: More docile and controllable, eh? You guys don't get out much.
Xavier Fitch: A train came through here about the time she escaped.
Agent: Is she that fast?
Xavier Fitch: She is that fast.
Preston Lennox: No one ever asked me to find anything they didn't want dead.
Dan Smithson, Empath: I feel sorry for you.
Preston Lennox: Yeah? That's great. I feel sorry for her.
Dan Smithson, Empath: I thought I was dead.
Preston Lennox: I thought you'd drank your last Long Island Iced Tea there, Dan.
Dr. Laura Baker: Yeah, I thought we all had. Hey, you okay?
Dan Smithson, Empath: Yeah, I'm okay. My pants are a little messed up, but I'm okay.
Dr. Laura Baker: She was half us, half something else. I wonder which was the predatory half.
Preston Lennox: The dead half. Let's get the hell out of here.
Answer: You could probably make a compelling argument that, as an alien-hybrid, Sil is stronger than a normal person and thus was just able to forcibly cut through the finger with the pruners by "crushing" it. Also, this is where good old suspension of disbelief comes in. The pruners might realistically have broken at some point, but it's a movie, so we can "forgive" this bit of unrealism because it creates a compelling scene.
TedStixon