I would advice you to write to the city archive of Pirmasens. If your grandmother was born in Pirmasens they should have documents about the family there. Ask for "Familienbogen" or "Meldeunterlagen" for the family. Perhaps they have a marriage certificate for the parents Friedrich and Maria Schnert and death certificats for both of them if they died in Pirmasens.
Don`t know if you get information about Louise Caroline because we have a very strict personal data protection law in Germany. You only can get information about people from today
-birth 120 years back
-marriage 80 years back
-death 30 years back
Perhaps they have emigration documents for her. If they owned a pub in Pirmasens there should be some information at the archive.
They surely demand a fee, ask for it.
Hope this helps,