When examining the relationship between Frances S. Osgood and Poe, one crucial detail that is always overlooked is the simple fact that after they met in March of 1845, she spent most of that year away from New York City. So far as her movements can be traced, (largely through her extant correspondence,) she was far from New York--and Poe--at least during May, July, August, September, October, probably June, and possibly November as well, spending much of that time in the company of her husband. She may have made flying visits to NYC during the year, but considering the rigors of travel in that era (just going from New York to Providence R.I. took a minimum of ten hours,) and Osgood's frail health, these visits must have been rare.
When Osgood admitted in her "Reminiscences of Poe" that her year-long acquaintance with him was largely through correspondence, for once she was not dallying with the truth. There must have been some sort of exchange of letters between them, as she was a regular contributor to the "Broadway Journal," but on his part, at least, they were all likely as bland and impersonal as this. If we trust the testimony of Sarah Helen Whitman (granted, always a dangerous thing to do,) Osgood herself admitted that Poe's correspondence to her consisted of mere notes exactly in the mode of that one surviving letter--cordial and polite, but extremely brief and lacking in interest. (Incidentally, Osgood's stupefyingly brazen claim that she and Poe wrote to each other only because of the urgings of his wife, who hoped that Osgood could use her "influence" to keep him sober, should be treated with the contempt and derision it deserves.)
And yet, Osgood's peripatetic ways are studiously ignored, with sloppy biographers and cheap novelists all insisting on portraying the two as being in each other's society virtually nonstop during the year 1845. Amazing.
A footnote: John Ward Ostrom, who edited Poe's published letters, gave the undated letter linked to above a speculative date of "late October 1845." Ostrom had no hard evidence for suggesting this date, and as Osgood was in Providence throughout that entire month, Poe's note to her--which indicated that Osgood was then in New York--must have been written at another time. All we can say is that this note--the only extant item of correspondence between them--was written sometime in 1845 or early January 1846.