The 1851 Dublin census index gives Mary Barnasconi (nearest I found) Eustace St Dublin.
Mary is also in Griffith's Valuations (again I have just the index).
Griffith's also has Thomas Barnascone in Wexford town, Civil Parish of St Selskas.
There may be other versions of the name.
Henry Shaw's 1850 Directory has Mary Barnasconi artifical flower maker, 19 Eustace St, St Andrews Ward, Civil Parish of St Andrews Dublin City. There was a Thomas Mitchell at no 15, same trade.
Couldn't find the name Darvell, the nearest was Deverell/Deverill.
I'm not sure if Mary came from Dublin, but have listed some "in case".
Pettigrew & Oulton's 1845 Directory
Jonathan Deverell Weighmaster Greenhide Crane 17 Bonham St.
Residence Booterstown Ave.
Another section gives W. Jonathan Deverell "Roseville" Cross Avenue Booterstown.
Mrs Deverell 4 Charlemount St Upper
Mrs Deverell Phibsborough Rd.
1851 Dublin City census
Hy Deverell 19 Anne St North Civil Parish of St Michan's Dub North.
Mary Deverell 29 Clanbrassil Terrace Parish of St Peter's Southside.
Henry Shaw's gives Mrs A. Deverell 29 Clanbrassil Terr.
Mat. Deverell 23 Monck Place Grangegorman Northside. (County) Outside the town boundary?
Edward Deverill 73 Meath St St Catherine's Southside.