Lobelia Sackville-Baggins is a Lord of the Rings Hobbit, one of the few, rare female characters in that series, and she's a nasty piece of work: a bitter enemy of Frodo and Bilbo, she is mostly depicted trying to either steal their stuff or buy it at deep discounts from them: she ends her days first imprisoned and starved, and then dead shortly after she's sprung.
Meanwhile, Victoria (Vita) Sackville-West was "a successful novelist, poet, and journalist, as well as a prolific letter writer and diarist" who was a contemporary of Tolkien. At the time, she was well known for her public complaints that she was not able to inherit her father's fortune because of sexist English laws (she was also Virginia Woolf's lover and was the inspiration for Woolf's book "Orlando: A Biography").
The supposition that Tolkien satirized Sackville-West comes from historian Dr Karen Carr, who points out that Sackville-West's life and campaign were both widely reported in the papers of the day, and that Sackville-West and Tolkien quite likely knew each other as they traveled in similar circles (Carr: "Tolkien hated people pointing it out. When the most famous inheritance case of your generation is by a woman named Sackville, and then you name the subject of an inheritance case on your novel also Sackville, that’s not a coincidence.")
Carr also says that while the real Sackville-West's life was much more interesting than Lobelia's, "Someone should write LOTR fanfic from Lobelia’s perspective."
That's a bit of a fraught project. Recall that legal threats from the Tolkien estate are the reason you can no longer buy Pat Murphy's outstanding, genderswapped The-Hobbit-in-Space novel, There and Back Again, a feminist masterpiece (though others have made similar efforts since).
I was today years old when I realized that Tolkien’s Lobelia Sackville-Baggins is probably a misogynistic satire on Vita Sackville-West, a well-known poet and letter-writer of his time who was bitter about being unable to inherit her father’s house bcs of sexist inheritance laws.— Dr Karen Carr (@Quatr_us) September 15, 2019