It APPEARS as though she is the daughter of Gustave SIMON, from the extract. Was he her step-father? Biological father? Where was her mother? Who was the 'other' person in the household?

As always, don't depend upon an extract. Search the actual record, if available. Marriage records should also be searched.

This may be a 'clue' to check the 1870 Census for Gustave SIMON. Couldn't find him in my index. Will make a trip to the library this weekend to double check - and search on the neighbors.

As for the second question...
Earlier civil marriage records are inconsistent from one parish to the next. In my searches at the Lafourche parish courthouse, there was a timespan when nearly ALL records had ages and parents, if known. Another range of years had neither. More recent records were a little more consistent. You never know.
When there is a question of IF you should/will send for the actual record, it is far better to be able to VIEW it first - but when that option is not available, obtain the record.
My personal opinion is to obtain all relevant records in your [re]search. Then, a [re]search does not have to be a re-[re]search !

[See my private post for one additional church record - and other options...]

Lynda M.