Rip Sadie, have some ?'s

Just to clarify, the dog didn't get caught on the kennels, I have the doc bob kennels with the roof so that isn't an issue. It looks like she went to attack the young dog (shes got some minor cuts on her face) and the young dog got a hold of her collar on the back of her neck. I don't know if she may of twisted while the cur had a hold and it choked her or what? Found out through my wife that the young dog is in heat. She shouldn't of been let out with the other ones if that was the case, but she didn't know. I've never had them fight serious outside the kennels, little bit through the kennel fencing but nothing major. Just doesn't really seem that easy for the young dog to do and doesn't add up to me, im stumped?