Strange that they are not listed and only shown on IGI
I have found 4 family trees with her name on, her marriage to Edward is there but shown as 2 dates, so whoever these trees belong to hasn't found her marriage, only on IGI it looks like
They were both full age when they married,
I do believe if one orders a cert on line at ONS, doesn't give a reference number, in this case there isn't one, includes as much info as possible, father's name and her rightful surname they will search 3 years, so one could ask for 1863 and 1864 I suppose, if they don't find the relevant information the money I do believe is returned, worth pursuing
Louisa Maud