I'm so sorry to read this. Its probably that the female is not spayed and she is going into heat. Dogs go into heat before they bleed so the owner might not know the signs.

Autumn got attacked by an offleash pug on our complex the other day so its not just pitties. It didn't make contact because she tucked her tail and ran back into the house before it could. The last time before that she was attacked was by a beagle and it did make contact and wouldn't let go of her ear.