Andrea, I have had a look on the IGI which is an index of births and marriages in the parishes of the UK, gathered by the mormons over decades and now accessible online at
www.familysearch.orgThere are few Selina Lunn's of the right sort of age and one is spot on.
Baptised 7th Feb 1841, Smethwick, doesnt say which church
Daughter of John Lunn and Elizabeth.
If someone beats me to it with this post then I hope you will at least bookmark the website I mentioned for future use.
Her siblings would appear to include
MARY ANNE LUNN -
Gender: Female Christening: 06 APR 1834 Smethwick, Stafford, England
JOHN LUNN -
Gender: Male Christening: 26 FEB 1843 Smethwick, Stafford, England
WILLIAM LUNN -
Gender: Male Christening: 10 FEB 1839 Smethwick, Stafford, England
Regards
Louise