I'm not pro Meghan but this is another one of the anecdotes about her which is easily twisted. I don't think she ever really claimed she didn't know 'how' to curtsey.
In her original telling of this on Oprah she said she was surprised that 'behind the scenes' you really did have to curtsey to the Queen each day's first meeting.
And she describes Fergie breathlessly rushing out to teach her how to do it. Which seems like something drama-loving Fergie would enjoy making a big thing about.
But as she'd trained as an actor and taken ballet lessons she would have known and executed various curtsies and bows over the years. Fair enough she might have wondered if there was a specifically British/royal way to do it.
But the main point of the anecdote, and again when she told it in the Netflix doc was her surprise at the formality of the custom.
What stood out for me both times she told this story is what a little toad Harry is, firstly for not preparing her properly with key protocols, and then as he sat by her side for her telling that story in both interviews he didn't speak up and back her up in any way with a "that was my fault, didn't realise it would be so strange for an American to deal with, just so used to it" etc etc.
I've always had the feeling that he was enjoying being a 'disprupter' in the family events and it was all about him and how he felt at bringing a glamourous outsider to smash all the rules. But he totally threw her under the bus to do so.