Wasn't Julia Longford Mellor born in Braddan?
IGI has: JULIA LONGFORD MELLER Birth: 05 FEB 1828, Christening: 29 APR 1828 Braddan, Isle Of Man, Father: JOHN LONGFORD MELLER, Mother: CHRISTIAN HOWARD.
So did her parents move to Wales after this?

I had a look for John Longford Mellor/er in a census to see where he was born, but couldn't find him in 1851. In 1841 John L Meller was 60, no occupation, and in Castle Rushen Gaol! B.England.
Christian 50 & Julia 12 were elsewhere in Castletown (Brian Lawson's index).

Sue