Hi Karen,
Re...
Do you have the marriage certificate of Alfred Henry HIGH?
Name: Eileen Nellie Allan
Spouse: Hy Alfd High
Marriage: 1914 - Victoria
"I have searched for Grandmother's birth (Eileen Nellie Allen) and have come up empty, which makes me think that perhaps she wasn't registered. Although on her wedding Certificate it states her birth was in Preston and the same on her death certificate."
What are the names she states for her parents, in 1914, when she got married?
What was her age at marriage?
Who were the witnesses? ... maybe they are her siblings.
Mary