Giblet has already posted about part of my following notes, but am posting the whole lot anyways!
The surname for Thomas varies wildly, Borwell, Burrill, Borrill, etc. I have written it in the following timeline as it appears on the image/index. You probably have most of this, but I am posting all my notes just in case! I didn't include Mary Ann's early life, as I assume you have all that from researching her mother Ann.
1851 census, Mary Ann Blow (16) servant to Thomas (55) and Ann (48) Borwell in Willoughton, Lincolnshire.
1853 Quarter 1, birth of George Blow registered in Gainsbro, no mmn.
The Lincolnshire Chronicle 08 April 1853
Mary Ann Blow, 15 years of age, of Grayingham, applied for an order on Thos. Borrill, of Willoughton, to support a bastard child. Defendant appeared in person, and also by Mr. Plaskin, his solicitor: an order was made for 2s. per week from the birth and costs.
(Note for above article): other newspapers running the same snip did not put an age for Mary Ann; her age of 15 is incorrect, so a mistype or the reporter had bad info?)
The Lincolnshire Chronicle 15 December 1854
Singular Death
On the 5th inst., an inquest was held at Willoughton, before C. H. Holgate, upon the body of Ann Borrill, the wife of Thomas Borrill, labourer, aged 52 years. Deceased was subject to fits, and had a girl of the name of Mary Blow to watch and attend upon her. On the previous day, there was a marriage at the church, to which Mary Blow went, leaving deceased sitting in her arm chair near the fire. After Mary Blow had gone, a travelling woman called at deceased's house, when she saw her laying upon the floor in front of the fire; she gave an alarm, and when Mary Herrick went into the house, she found deceased laid in front of the fire and her clothes on fire, and face embedded in paste, she having upset a pancheon of paste when she fell out of her chair. The fire had not reached her person, but her mouth and nose were filled with the paste. The jury were of opinion that deceased had fallen out of her chair in a fit, and by upsetting the pancheon of paste was suffocated. Verdict accordingly.
1856 3rd Quarter, death of George Blow registered.
1860 1st quarter, registration of birth for Mary Ann Borrell in Louth, no mmn
1860 1st quarter, marriage of Mary Ann Blow and Thomas Burill, Gainsbro'
1861 census - Willoughton
Thomas Borrell (65), Mary Ann (26) and daughter Mary Ann (1)
1871 census Willoughton (daughter is now surname Blow and Thomas and Mary are "Barrell")
Thomas (75), wife Mary (36), daughter Mary A Blow (11)
1875 2nd Quarter, death registration for a 79yo Thomas Borrill, Gainsbro'
1881 census - Willoughton
Widow Mary A Borrell (45, but something is written over 45), a charwoman, with a lodger Isaac Thompson (66)
1891 census - Willoughton
Maryann Borrill (transcribed at Anc as Bouill), head, no occ. and lodger Isaac Thompson (76) still there.
1892 2nd Quarter, death registration for Isaac Thompson, age 76, Gainsbro'
1901 Ashby, Lincolnshire
66 yr old Mary A Borrill , born Kirton, visiting household of James L. Thompson (46)
(James L Thompson was the son of Isaac Thompson)
1910 2nd Quarter- there is a death registration for a Mary Ann Borrill, age 75 in Gainsbro'
I am curious as to what happened to the daughter, Mary Ann Blow/Burrill, born 1860, but there are far too many marriages/deaths that could fit either surname.
As for the death of Thomas' wife Ann in 1854...... all I can say it is unfortunate that there wasn't the forensic tools that we have today. The verdict could have been much different!