Isabella Arnold, nee Smith, was baptised in Leyburn, Middleham, Yorkshire, on 15 April 1811. Her parents were Francis and Ellen Smith. Her marriage with Thomas Arnold took place in Leyburn during the 2. quarter of 1847.
The 1841 census tells about an Isabella Smith who was born in 1811 and lived in Guiseley, Kirkstall, Leeds, Yorkshire.

Lieutenant-General Sir George Arthur, 1st Baronet KCH PC (21 June 1784 - 19 September 1854) was Lieutenant Governor of British Honduras (1814-1822), Van Diemen's Land (now the State of Tasmania, part of Australia) (1823-1837) and Upper Canada (1838-1841). He also served as Governor of Bombay (1842-1846).
He was born in Plymouth, England and was the youngest son of John Arthur, from a Cornish family, and his wife, Catherine, daughter of Thomas Cornish. More information on Wikipedia.

Unfortunately, we couldn't find information about Miss Arthur, probably Sarah Arthur.