I can last find her in 1891 married to James Philip, 1901 James is a widow living with his brother.
Wonder why she would go back to Canavan tho?
Is this Mary on the 1871 census. Family headed up I think by James Canavan and Ann Brogan:
James Cannavan 53 coal miner b. Ireland
Ann Cannavan 48 b. Ireland
Thomas Cannavan 23 coal miner b. Old Monkland, Lanarkshire
Sarah Cannavan 14 b. Bothwell, Lanarkshire
Margaret Cannavan 9 b. Bothwell, Lanarkshire
Mary Cannavan 19 Grandaughter b. b. Bothwell, Lanarkshire
Address 13 Brick Row, Old Monkland Eastern District
If this is Mary with grandparents, then her mother could well have had the surname of Brown. She could also be illegitimate and used her grandparents' names as her parents on her marriage registration. Maybe a mistake crept in when remembering grandmother's maiden name. Hard to say and supposition really for now.
Can't easily see the Canavans in 1861 so far to see whether Mary shows with them.
Monica