I had never heard of the Porter sisters, but I just went and sampled some of their work on Project Gutenberg, and I suspect the main reason that they are forgotten is that their books are melodramatic and not especially well-written. A taste:
> How often, as a cloud obscured for an instant the moon's light, and threw a transitory shade across the path, did her heart bound with the thought that her watching was at an end! It was he whom she had seen start from the abrupt rock! They were the folds of his tartan that darkened the white cliff! But the moon again rolled through her train of clouds and threw her light around. Where then was her Wallace? Alas! it was only a shadow she had seen! the hill was still lonely, and he whom she sought was yet far away! Overcome with watching, expectation, and disappointment, unable to say whence arose her fears, she sat down again to look; but her eyes were blinded with tears, and in a voice interrupted by sighs she exclaimed, "Not yet, not yet! Ah, my Wallace, what evil hath betided thee?" [0]
The author may take comfort from the fact that Scott's work has also fallen dramatically in popularity and is probably unknown even to most well-read people these days.
I also just cited Sir Walter Scott as a possible model for Crichton & Grisham's reputation 200 years from now. He's also not widely read anymore, for maybe the same reason: this breathless, overblown, wordy prose. No one likes that these days.
Look, they were popular at the time, which sort of belies the notion that women were deliberately suppressed. Even Napoleon had heard of them:
> Napoleon himself understood the dangers the sisters’ books posed to him: He banned Jane’s novels from publication in France, presumably because they might encourage popular uprisings.
There are millions of would-be writers who'd kill for this sort of fame, even if they're forgotten after they're dead.
Ruled maybe. But they weren't neither the first English authors to write historical novels (The Unfortunate Traveller by Thomas Nashe was published in 1594), nor the best.
It's ridiculous to start inventing domains where women were first.
Edit: I'm not one to complain about downvotes but please, in keeping with the glorious legacy of the titular scribes - which I'm sure you've heard of before this was posted and whose works you have no doubt devoured - use your words.
Incidentally, the title and entire premise the article hinges on is a singular quote from an obituary in the The International Miscellany of Literature, Science & Art, Volume 1, Nov 1850.