I'm still wondering why we didn't find a baptism for Harriet Mountford...  

After much searching with no results, I saw on the 1851 Census that the approximate birth year was 1838, and it occurred to me that it could be listed on FreeBMD (since it could be after 1837)  

  [It also says she was born at Oseworth, Staffordshire].
I found 
3 possible births for Harriet Mountford:
SEP 1838   Harriet Mountford at Stoke on Trent,
DEC 1838   Harriet Montford at Newcastle under Lyme, and
DEC 1838   Harriett Mountford at Wolstanton.    
