According to this interview, Hermione no longer has a sister in canon either.
The relevant Q and A:
Does Hermione have any brothers or sisters?
No, she doesn’t. When I first made up Hermione I gave her a younger sister, but she was very hard to work
in. The younger sister was not supposed to go to Hogwarts. She was supposed to remain a Muggle. It was a sideline that didn’t work very well and it did not have a big place in the story. I have deliberately kept Hermione’s family in the background. You see so much of Ron’s family so I thought that I would keep Hermione’s family, by contrast, quite ordinary. They are dentists, as you know. They are a bit bemused by their odd daughter but quite proud of her all the same.
Said sister wasn’t present in the Grangers’ house during the Christmas meal sequence, so it’s possible she doesn’t exist in the Methodsverse.
According to this interview, Hermione no longer has a sister in canon either.
The relevant Q and A: