Tracing Fife LYALL ancestors

I live in New Zealand & I have been researching my husband's paternal LYALL ancestors for some years. His 2x great grandmother, Jennet LYALL, (b.27 Sep 1825 Templehall, Aberdour, Fife) had an illegitimate dau. Janet LYALL (b.4 Nov 1849 Kirkaldy, burnt Is, Fife)... my husband's great grandmother. Janet emigrated to Otago, NZ in the early 1860s. Her mother, Jennet LYALL does not appear to have married & Janet's birth father is unknown. Jennet appears in the following Scotland Censuses: 1841: 15 years, living with her parents, Robert & Catherine LYALL in Mcbalmile, Aberdour, Fife; 1851: 25 years, working as a housemaid in the Edinburgh household of Alex & Caroline CUNNINGHAM; 1861: 35 years, working as a domestic servant in Edinburgh in the household of Lewis WALLACE. I have 2 possibilities for the 1871 & 1881 Census for Jennet but the birth place is different (Ceres, Fife) & her age incorrect by 3 years.
I can't find a marriage or death for Jennet that are definitive. I have searched using Scotlands People, Ancestry, FMP, Family Search plus other Scotland websites.
My query is: Are there gaps in Fife BDM records which may account for my difficulties? Are there any other records I could use or resource archives to contact?
I'd really appreciate it if someone could help.