If you look at the original copy of the census, you will see that Mary Ann is married to "Lemuel" not Samuel. In the name above his Louisa is written and the "L" in her name looks exactly like the "L" in Lemuel. At the top of the page, the census taker wrote the words Tin Smith with Smith capitalized. The "S" is distinct and nothing like his letter "L"
Mary Ann is the wife of Louis Lambert Pitre, married in 1848. Mary Cicotte, profiles will need to be merged
"United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MF85-RW9 : 12 April 2016), Samuel Peters, Detroit, Wayne, Michigan, United States; citing family 1607, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).