Hi Again Chris.
Margaret Nivin married George Dallas at New Monkland Aug 1836.
https://familysearch.org/pal:/MM9.1.1/XT1W-G4JMargaret Niven married Alexander Lamond at New Monkland Jul 1840
https://familysearch.org/pal:/MM9.1.1/XT1W-XJ6Suspect this is the same woman - George Dallas probably died

1841 Census Graham Street, Airdrie , New Monkland
Alexander Lamond age 25 Coal Miner born outside Census County
Margret Lamond age 25 born Lanarkshire
Martha Lamond age 4 born Lanarkshie
George Lamond age 3 born "
Robert Lamond age 5 months born "
I'm sure this is Martha in 1841 on the Census with her stepfather's surname.
Margaret Niven and George Dallas also had a son George in 1838 -https://familysearch.org/pal:/MM9.1.1/XT1W-XJ6
Can't find a birth for Robert Lamond but would assume he was Alexander Lamond's son going by the dates.
And can't find any of the family ( bar Martha lodging with the Roberts and with the 2 Nivens) on the 1851.
Looby