Her words say nothing about granny giving her a tutorial.

What I'm reading is a granny that wanted Jada to avoid some of the baggage most women of previous generations carry.

I can sorta see how you might think "how to" but, in practice, most people figure out how to masturbate on their own even though nobody (used to) admit that they were doing it at all.

And if you think of the context of that video, it fits in perfectly with baggage that Jada's mother felt she was saddled with most of her life surrounding sex and masturbation.