I am the person that put together the St. John's Lutheran database, and I have photocopies of all the records through 1999. HER death record in the church book shows her named listed as: Dorothea Schmidt geb. Holst
But on HIS death record in the church books she is listed as: Maria Dorothea Sophia geb. Ohlson
I transcribed the records "as is" so they would be true index of what was written in the church books... there are many errors inherent in the records themselves, from my inability to make out the old German script in some cases, and likely from my human error - although we did have others proofread, it was a lot of data. :-)
On the 1819 Mecklenburg Census (on Ancestry.com), there are Holsts, but don't see Ohlsons.
Also checked www.familysearch.org
and found many Holsts in the Rostock and surrounding area, and I also found the name Ohlson in Mecklenburg, but very few.
BUT - I did find the Schmidt family for you and it shows her as a Holst!!
It looks like Blankenhagen in Ribnitz district near Rostock is where several of their kids were born... and you're in luck!! The LDS Church has microfilmed church records there from 1704-1894... Films 68963-68967.
But, better luck... many of these records have already been indexed online - for example, I see that Johann Joachim Christian Schmidt was born in 1805 instead of 1804 as the St. John's records state. His Parents were Friedrich Niclas Schmidt and Eva Ilsabe Eggers - they were married Willershagen 19 Feb 1802 and Eva's father's name was Joachim Eggers.
There are more children and other family members listed and you will find MUCH more in the microfilmed church records.
Other towns near there referenced with this family are Niederhagen & Willershagen, with Willershagen being most prevalent and very close to Blankenhagen.