First name, year of birth ca 1843, date of death, place of burial from billiongraves.com website for Greytown Cemetery.

Brian of nzolivers.com has found that Louisa, husband Samuel, and two children emigrated to New Zealand on the “Golden Sea” in 1874. Passenger record:
https://familysearch.org/ark:/61903/3:1:S3HT-DR43-H42?cc=1609792
Sailed London 29 January 1874
Arrived Wellington 1 May 1874
Samuel 35 years Sussex Bootmaker
Louisa 30 years
Jane 2 years
John 6 months

The above places year of birth as circa 1844.

Search Results of official BDM Historical Records ‘Louisa’ as the mother of the following NZ-born children:
1875/9161 Gates, Ernest Louis
1876/11311 Gates, Frank
1878/14616 Gates, William James
1880/5341 Gates, George
1881/11799 Gates, Ada
1884/6932 Gates, Gertrude Jane

Maiden name of ‘Mitchell’, year of birth as 1844, date and place of marriage, from research file04 in June 2014.
This file also lists Ernest Lewis as a son.

Brian found this Death Notice for Louisa on Papers Past website:
WAIRARAPA AGE, VOLUME XXXII, ISSUE 10679, 6 JULY 1912
PERSONAL
The death is reported at Grey town of Mrs Gates, wife of Mr Samuel Gates, at the age of sixty-nine years.