Because I am a post-95 generation, most of the girls around me are post-90 generation, some are like you said, some are worse, calling themselves grandma, haha, of course, this is all a joke, don't take it seriously. As for them, they call themselves old aunts because their age is embarrassing. Children call themselves little sisters, but if they call them aunts, they feel that they can't accept them for a while, and time passes too fast, so they laugh at themselves and their old aunts. To tell the truth, they are always there, just joking to make themselves and others happy.