A traumatized boxer

This afternoon as I was driving home from skating and running errands, I saw a dog on the side of the road not too far from the entrance to my neighborhood. Roadkill kills me. I can't stand the sight of a dead deer or raccoon, and the sight of a dead cat or dog breaks my heart. I quickly drove to my house, grabbed one of my dogs' leashes and went back to rescue this abandoned dog. When I finally caught up with it, it was clear that this was a female boxer, spayed, perhaps around a year old and she was terrified. She barely let me come up to her, but finally gave in. She had no identification, only a shoestring tied around her neck. I managed to put the leash on her, got her in my car, and drove her back home where she's been in my fenced-in backyard since around 3 PM. I have an ad on craigslist, several posts on Facebook and have called both the boxer rescue and the local SPCA to report her. I made the mistake of trying to bring her inside to get warm, but my ferocious dachshunds traumatized her. They both bark incessantly at her and Quintin tried to attack her several times. I really wish I could bring her in out of the cold, but she is so scared of Quintin that she refuses to come back inside. Tomorrow I'm going to go see if she is microchipped and hopefully reunite her with her owner. One person in the neighborhood who is already a boxer owner has potentially agreed to take her if no one comes forward. She is a really sweet and smart dog. I wish I could keep her, but that would never work.