Isabella Charters age 28 born Galway, wife
I wonder whether the passenger list was compiled by someone who was more familiar with place names in Ireland than in Scotland, and who thought that Galloway must be a misspelling of Galway?
I see that Isabella is described in the 1851 census as a widow, aged 29, pauper, born Kirkcudbrightshire, Crossmichael. If her age is accurate that puts her DoB between 30 March 1821 and 29 March 1822.
So on 6 June 1841, the date of the 1841 census, she might have been just 20, or she might not yet have been 20 and, because over-15s' ages were supposed to be rounded down to the nearest 5 years, recorded as 15.
There is a family in 1841 at Hill, Balmaclellan, Kirkcudbrightshire comprising James Hyslop, 55; Isabella Hyslop, 45; William Hyslop, 20; Isabella Hyslop, 15; and two servants. However all four Hyslops are said to have been born outside Kirkcudbrightshire.
There is a 15-year-old Isabella Hyslop in 1841 at Barnspark, Crossmichael, with Jannet Hyslop, 60; Jean Hyslop, 20; and Charles Tait, 6 months.
There's a 15-year-old Isabella Hislop, not born in the county, in the household of Barbara Johnstone at Earlston, Berwickshire, with Eliza Hislop, 13; John Hislop, 10; and William Hislop, 8.
Also four 15 or 20 year old Isabella H*slops, not born in county, listed as servants: one in Rutherglen, one in Traquair, one in Ettrick and one in Straiton.
Information from FreeCEN
https://freecen1.freecen.org.uk/cgi/search.pl