I think I have her birth source:

Lilian Mary Nicholls
Year of Registration: 1874
Quarter of Registration: Oct-Nov-Dec
District: Gloucester (1837-1937)
County: Gloucestershire
Volume: 6a
Page: 289

From that I ought (hopefully) to be able to figure out who her father was. This is pretty much an aside to the main issues but i'll post what I find when I get the certificate.