There's hair in my dog's stool..?

I was just out taking our three month old er spaniel, Holly, on a walk. Everything had been going normally until she tried ping stool. There seemed to be a rather long piece of hair (obviously not her own) attached to it and it wouldn't come off. She promptly started crying and sprinted back up the stairs to our apartment. Within that time the stool somehow came off, but I didn't catch where and wasn't able to locate it. The piece of hair is still there and when one of us attempted to gently pull it out, she yelped and jerked away. Any advice?