After Poe's death, Maria Clemm believed much of the negative things written about Poe by Rufus Wilmot Griswold, partly because Griswold had evidence to prove it. It turns out, however, that Griswold forged many of the documents that served as back-up for his concerted character assassination on Poe. Reading Griswold's lies, Maria Clemm lamented: "To think of that villain Griswold dragging before the public all my poor Eddie's faults and not to have the generosity of speaking one word of his good qualities."
That's why Maria Clemm was particularly grateful to the people who came forward in defense of Poe. One such defender was Henry B. Hirst, a friend from Philadelphia. Clemm wrote to him (using black-bordered "mourning" stationary) on October 23, 1849, thanking him for his kind words. As she wrote, "God bless you for doing justice to the memory of my own dear Eddie."
Henry Hirst is a strange character in the study of Poe. The two were introduced in Philadelphia some time in the summer of 1839 (by, of all people, Thomas Dunn English). The two became friends during Poe's tenure in Philadelphia. Though a minor poet at best, Hirst did his best to make money from writing. He even wrote a biography of Poe, published in 1843, in the Philadelphia Saturday Museum. He also reviewed (rather caustically) Griswold's The Poets of Poetry of America in that same newspaper. Poe's own published reviews of Hirst's poetry isn't particularly flattering, though he also accused T. D. English of plagiarizing from Hirst. Poe also though Hirst was stealing his own poetry, but those accusations weren't published in Poe's lifetime ("I do not object to him stealing my verses," Poe wrote; "but I do object to his stealing them in bad grammar. My quarrel with him is not, in short, that he did this thing, but that he has went and done did it."). In fact, Hirst at one point suggested that he was the true author of "The Raven" (who wasn't trying to steal Poe's thunder?), the only evidence being that he owned a pet raven for a time (well, so did Dickens).
Later, after Poe's death, Hirst became a heavy drinker, and it was well-known that he was addicted to absinthe, and soon went insane. The association between Poe and Hirst, especially his defense of Poe and reference to "rollicking" companionship made by John Sartain, led to the rumor that Poe was a heavy absinthe drinker himself (something I still hear about on occasion; a quick Google for "Poe and absinthe" proves there are still people out there perpetuating the rumor). However, as the Edgar Allan Poe Society (Jeff Savoye?) has proven, Poe was almost certainly never an absinthe drinker.