So you kill her. Exactly why and how is that supposed to keep her friends from taking revenge? Seems to me it would give them more motivation.
Here's some news. You're either a wolf or a sheep. I choose to be armed and if someone were to break in my house and I felt threatened, then they'd die from dog bites or gun shot wounds. Nobody is "sneaking in" and if they kill my dog, well then I think you'd be willing to kill me and I'd be afraid for my life.
I can guarantee that I'd only give my name, that I was afraid for my life or the life of my family then only talk to my lawyer after going to the hospital to "get checked out".
I'm glad the old guy is alive if the choice were between the two pieces of crap that broke into his house or him...... I chose him.