Wow, Kristin--this is just amazing! I love how you describe your line of thoughts regarding this mystery, and it certainly seems intriguing that she went from being widowed in east London with two young children in 1851 to five years later arriving in New York... and a short 9 months later, settled down in Michigan. Indeed, it seems there must have been some kind of match-making happening of some sort.
I have a New York Times subscription, and was able to view an article from the 1800s entitled, "Marriage Made Easy: Successful Agencies of Past and Present Times" from Sunday, 27 Jun 1886. That article begins:
"PARIS, June 15 -- An American reporter some months ago gave a humorous account of his interview with a matrimonial broker in New York. Some little time before that Mr. Charles Payne, an English journalist, told of his efforts to learn the secrets of like agencies in London, as he affirms, aesthetically, although his book leaves you with the impression that had any one of the more or less lovely beings who answered his call realized his ideal, he might have struck a personal bargain and have withheld his revelations, especially as, on the whole, his conclusions are not unfavorable to the institution itself."
The article continues on in that general vein providing a kind of introduction to the topic, and then gets more specific about what was going on in the mid-1800s:
"But all these were mere skirmishes; none of them did anything regularly or neatly unti lM. de Foy came upon the stage, and to him, unquestionably, belongs all the credit of the invention as it exists at present and which dates from 1842, when all France was astounded by an advertisement in every newspaper, metropolitan and provincial, to the effect that he had opened a matrimonial bureau, of which the motto was 'Celerity and Discretion,' and where all classes, creeds and fortunes could be accommodated."
So here we seem to have verification of a real match-making program that was operating at a noteworthy level in the 1840s on. Very interesting!