so sad I can hardly take it

This is Pixie and this is the important background information you need to know:
1. She is my dog (Charlie is Alex's dog)
2. She is an unspayed four-year-old Siberian huskey and Pit Bull mix
3. She is terrified of our cats - especially Enjouer - I've had to rescue her from him before when he got her backed into a corner
4. She is super smart (taught herself to fetch) and super energetic (taking her for a walk you realize why huskies were taught to pull sleds)
5. She is insanely protective of her family, including the other animals, Alex, Wendy, myself and our house and yard - she's left my several gifts of dead animals over the years (moles, snakes, rats, squirrels, etc.) which had the audacity to come into our yard without her permission
So here's what happened:
Last night I put the dogs out onto the back porch to get them out from under my feet so I could fix Wendy dinner. Alex heard Charlie barking like a maniac and went out back to yell at him to be quiet. He was out for longer than it normally takes to yell, "Hush up" so I peeked out the window to see what was keeping him. I saw him whacking on something with a broom and then he nose-dived to the ground behind our big tree. I called to him, "What's going on?" And he screamed back to me that Pixie had gotten a cat.
It must have been a stray that wandered into our yard, but when I rushed over to see if I could help, all I could tell from looking at the poor animal was that it most likely was not going to make it - it had parts that should have been on the inside visible on the outside. It was hurt quite badly. Alex told me after it was all over that at first he thought she had a toy doll someone had tossed into our yard the way she was shaking it around, then he realized it was alive and thought she'd somehow gotten ahold of a puppy. He ran over to Pixie with the broom, trying to get her to let go of it without causing further injuries to either animal, and that's when he realized it was a cat.
Alex yelled at me to keep away from the injured cat once he'd gotten it free and asked me to bring him Pixie's collar and leash. When I returned it was just in time to see the wounded cat jump over our fence and run away. Alex hauled Pixie inside and then drew my attention to Charlie. We still aren't 100% sure how it actually happened because Charlie was already limping and crying by the time Alex got outside, but somehow Pixie bit Charlie and hurt him pretty bad. We know it had be an injury caused by her and not the cat becasue the bite marks are too big for a cat. Charlie is still limping and Alex has insisted we take Pixie to an animal shelter.
I'm not disagreeing with him - I understand that living in a house with another dog, three cats, and a small child that one strike in the biting zone means you are out (all animals included). I know that being attacked by dogs when Alex was little doesn't help him to feel any pity for a dog that bites. I know that he is making a hard decision to keep Wendy and four other animals safe.
But...
She's my puppy. She thought she was doing right, protecting us from a strange, intruding animal. I know she only bit Charlie by accident, that she was caught up in the frenzy of protective fury (and yes, I understand that it just as easily could have been Alex, or Wendy who was in the wrong place at the wrong time near Pixie's frenzy) She won't understand why we've suddenly left her in a strange places with scary new smells, new people, and other animals. She'll be scared and confused and as an adult dog may never get adopted again - especially if anyone finds out she bit another dog.
I'm just so sad, and I can't think of anyway to make this any better.