http://www.rootschat.com/forum/index.php/topic,479268.0.html - linking over so people can see what has been found
This would also fit with:
"Female" Langley b. Mar 1850 quarter Lewisham (Eleanor)
"Female" Langley b. Dec 1851 quarter Lewisham (Emma)
Edward Langley b. Sep 1853 quarter Lewisham (son)
Edward Langley d. Jun 1854 quarter Lewisham (the father?)
http://www.rootschat.com/links/0vhw/ - says that Mary Maria's husband was the late Edward Langley of "Ro'mpton Surrey" - copied to English papers. (interesting given the reference to Roehampton in the other thread)
Does the 1864 marriage give any hints e.g. who were the witnesses?
The real mystery is this:
From the English census, Mary was 28 in 1851, so in her early 30s when her husband died leaving her with four kids, the youngest just a baby, and then nearly ten years later she emigrates - why? Were there relatives there? It just seems a huge risk for a widow to take on her own with four kids, none of whom were old enough at the time to be much help in supporting the family.