This question was posed earlier at:http://www.rootschat.com/forum/index.php/topic,364312.0.html
A RootsChatter mentioned that Pedigree Resource File in response.
Also, Callywoods mentioned an Isabella Campbell SIMERS born 1878 and wondered whether that might be her.
Callywoods, have you downloaded that birth certificate from ScotlandsPeople in order to find out the names of her parents?
Though, from the 1881 census, Isabella's family looks to be the following SUMMERS family in South Knapdale, Lochgilphead - James 36 Head, Gardener, b Ireland; Eliza 29 Wife b Ireland; Patrick R 10 b Renfrewshire; Margaret 8, James 6, Mary 4, Gabella (sic) C 2, William 6 mths - all b South Knapdale. The 1871 Renfrewshire birth of Patrick Robert SOMERS,mother's name MURPHY is in the IGI. As are the 1872 and 1874 births of Margaret and James SIMERS in South Knapdale, mother's name MORPHEY(S). The 1870 Renfrewshire marriage (SOMERS) is also in the IGI.
In 1891 there are two further children, Eliza and Catherine, and father James is not around.
PS: The death of Fortable MCKENNA other name SIMERS in 1958, birth year 1876, is on SP.