u/Glitz_Whisper4750

So, I'm taking care of my sister's dog while she recovers from a surgery, I have been taking care of her dog for about two months and everything has been okay until yesterday, let me tell you a little bit about her dog, he is a blue heeler and he was used to live with a shepherd, sadly he fought with him really bad and my sister solved the issue separating the dogs, but still he can’t see that shepherd because he gets reactive and starts a fight, anyway the blue heeler never any potential fight with his sister (ofc he had fights but not aggressive) until yesterday I was feeding both of them and they finished but some noise from outside alerted the blueheeler and started a fight with my dog, my mom tried to interfere but somehow she ended up in the floor, we separated them and keep them separated at night, at the morning we put them together again and everything was okay, I was feeding them and the blue heeler finished eating faster than my dog, he then went with my dog (she was eating) and then the fight started again.

Idk what to do now, I have them separated now but for me is not human to have them that way I need help