I just read that justice, in many states in India, descends much swifter upon those who slaughter a cow than those who rape a woman. It made me wonder if the cow was originally considered sacred because the so-called Hindu "goddess" was using the animal as a proxy, for her to remain anchored in the physical, not having earned the right to life?*
Your interpretation is a good guess and may be a secondary cause. The first cause started out as an insult.
Thousands of years ago, what became known as India, was given to Isis by her grandfather to be her domain to rule over. She was a stunning beauty and had her main palace in the northern area of India (she had a smaller summer palace in Nepal). As she grew older, the human citizens very unkindly called her, "the old cow". So she declared that cows would henceforth be regarded as sacred. For ceremonies where a sacred cow was sacrificed to the goddess, she wore a horned (cow horns) headdress.
She had first been revered by her people, but then they turned on her and she became ridiculed. Eventually she left for her Nepalese palace where she laid her body down (under a meter-wide, body-length triangular crystal) and died. (I can't remember what purpose the crystal served.)
But Isis was human [humanoid] right, pretending to be a goddess?† (Since her grandfather – Anu – would've been Anunnaki.)
She was Anunnaki. And yes, she found humans much more manageable if she deified herself. She really promoted the goddess image and had temples built for herself. It worked so well that the other Anunnaki emulated that idea. Enlil became "God the Father" and he's been able to fool most of the world ever since. They're all gone.