Она скорее всего доминантная из этих двух собак, а они всегда едят первыми - так что собака вела себя правильно, она просто офигела от того что какая-то чужачка сходу в альфы метит

как-то так:
https://zoomroom.com/admin/introducing-a-new-dogDogs do not live well in democratic societies, and so it’s important to respect the hierarchy to avoid aggression and confusion. This means that you should feed and pet the dominant dog first – even if it’s the new dog. Relinquishing the post of top dog can be hard on the older dog, but is usually harder on the owner. If you feel guilty, take your older dog for frequent walks by himself. But around the other dog, you must respect the hierarchy or the new arrival will try to assert himself even more forcefully, which often leads to aggression. When everyone understands the order, no one fights.