Helen was born in Kirkcudbrightshire 1771 and died 21/06/1844 .
If your source for Helen's date of birth is her age in the 1841 census, be aware that in 1841 adults' ages were supposed to be rounded down to the nearest 5 years, so a person aged 60 could have been born any time between 7 8 June 1766 and 7 June 1771, assuming their age is accurate.
And just because there is only one possible candidate in the surviving indexes does not mean that it is necessarily the right person because large numbers of records, if they ever existed, have not survived.