I'd like to think she did it to protect me. Aside from parents and grandparents and siblings, no one in my life would do such a thing. Everyone else (except possibly one or two other people I also like to think would do almost anything to protect me but prefer never to know for sure) has entered my life with an agenda to use and discard. But in this case it's simply a matter of instinctive drive to kill. Sky likes to kill, having already wasted an armadillo, two possum and now two copperheads, that I'm aware of. She killed the copperheads today while I was trimming the verge. I had been reaching into that same verge barehanded to pull weeds and grass barging into growing space of vegetables planted there three weeks ago.
Luckily today the electric trimmer action drove a pair of copperheads out of the verge into Sky's territory instead of toward me with intent to bite. Sky attacked them both upon sight and made careful but short work of them. At least, I thought she had been careful when I checked over after the incident and both snakes were dead.
But her left lip is swollen now. I just discovered it a few minutes ago while petting her during my usual up-and-about time in the wee hours of the morning. She's always part of the ritual pre-dawn check around the property outside before first cup of coffee and occasional pre-breakfast snack.
It's tender, but she's not having any problem breathing and seems as energetic and playful as she always is. And she's still guarding the two dead snakes, treating them as though still alive and dangerous with quick, biting strikes. I'll check her after sunup again to make sure she's going to be okay and take her to the veterinarian is she's showing any signs of distress.
UPDATE: Three days later and she's fine. The next morning the swollen lip had shrunk back to normal and the only sign of the snakebite was a scabbed-over pair of puncture wounds. Seeing me coming into her territory, she was eager to play keepaway with her favorite toy.
A natural born killer.