I'm one of the probably very few people on here who has never read a single word of JKR's fiction. All I know of her is her pro-women activism, her philanthropy, and those very very witty tweets
That's enough to make me think that she is an admirable person, a tireless defender of the undefended, and someone who has made a huge contribution to social justice when it was/is under threat.
I have to take issue with your description of her review of NS's Frankly as 'personal and vicious.'
I thought the reviews by JKR and K. Stock were careful to avoid being personal and vicious, though the temptation - and the ammunition provided by material in NS's book - must have been strong. I'm sure they knew their reviews would be scrutinised closely for anything personal or below the belt.
The reviews were about what NS has said in her book, and how it is at odds with what NS did in her public life. Not, note, her personal life. Her public, political life, which was extraordinary, and extraordinarily damaging to women's rights, so hard-hitting criticism, including from JKR is just par for the course.
Hard-hitting, fact-based criticism of an apologia about a politician's controversial and ultimately failed career is not the same a personal and vicious attack, and I don't think it is correct to describe JKR's review as such.