Sarah, If you haven't looked at the obituaries in Manx Notebook, try following this link
http://www.isle-of-man.com/manxnotebook/mquart/mq14168.htm#173
This is listed as " Mrs Clegg (of Liverpool )"-----Catherine Clegg nee Clague 1820-1913, older sister of your great grandfather Thomas Clague b 1822.
Below is the census entry for your g g grandparens' household, Arragon Mooar:

1851 Santon, IOM
Arragon Mooar Hsehold #17
Thos Clague Head/Mar/61/Farmer 135 acres /IOM Arbory
Esther Wife 59 / Rushen
Richard Son Unm. 30 / Rushen
Esther dau U 20 / Santon
Jane dau U 17 Scholar / Santon
Marg't dau U 15 Scholar / Santon
Alice g.dau 3 / England
Philip Clague Servant U18 Ag Lab IOM/ Malew
Thos. Shimmin Serv't U 17 do
Jas. Corlett Serv't U 15 / Santon

The " Alice g.dau" aged 3 was Alice Clegg 1847-1931, and she was my great grandmother. Alice's parents were William and Catherine Clegg. The picture of them in Catherine's obituary is from one of Alice's treasured possessions which has been passed down through the family. It's an ambrotype photograph in a gilt pendant, and judging by its condition, it was well used.

In the 1851 census, your g grandfather, Thomas Clague b 1822, was staying with William and Catherine Clegg in Liverpool. Also in the household was brother Robert b 1827.

1851 St. Simons Ecclesiastical district of Liverpool
18 Lime Street
William Clegg Head Mar 31 bricklayer & builder IOM
Catherine Clegg wife mar 30 IOM
Esther Clegg dau u 8 scholar Lancs, Liverpool
Catherine Clegg dau u 6
William Clegg son u 5
Thomas Clegg son u 1
Robert Edward Clegg son u 3 months
Thomas Clague brother-in-law 28 unmarried, tidewaiter, IOM
Robert Clague brother-in-law u 23 , cooper, IOM
James Hall lodger mar 76 bracemaker Ireland
Elizabeth Clinton Servant 20 house servant IOM

3 year old Alice is listed as Alice Clague in the Arragon Mooar household, while her parents, brothers and sisters are using the Clegg spelling in Liverpool.