Why would you kill her? It sounds like she was protecting her babies, and you probably startled her. I am VERY careful around nursing moms - their protective instincts kick in. I've been lucky not to have been bitten as badly as you have, but I have been given some VERY stern warning nips - hurt like heck, but didn't break the skin. I certainly wouldn't reach in when she's laying on her back taking a snooze. I generally talk to them to wake them up and encourage them to come to me, not me just reach in to pet.