You can see that you are working with a family name that will have variations of spelling.
You are not seeing a birth for Margaret Jane LEMIN.
Someone, somewhere along the line has to just spend the money on the marriage certificate.
Margaret Jane is likely born with a different family name, so information about her parents, as named on the marriage certificate, will assist you to find her origins.
"...her mother's name as Emma (no other names but perhaps Jane Rolf)."
If you are offering a piece of information, you need to support it............who is Jane ROLF and why do you think she might be related to Margaret Jane?