You're probably spot on.  I'll give you my example.  All her young life, my nmom was pretty and exuberant, the life of the party.  Everbody loved her. Even after my sister and brother were born, she was still relatively slim.  When I was born, I  was ridiculously underweight.   My nmom gained 65 lbs during her pregnancy with me, weight she couldn't shake after I was born.

But everyone loved me.  I was a social baby and toddler. However, nMom took exception to that. She didn't like that I,  through no effort whatsoever on my part, was popular and liked, while, at least in her narcissistic mind, was now fat, unattractive and unpopular.   Her vanity made her, I believe, despise me.  I will carry her abuse of words and actions with me until I die.