I also have ancestors from Kreuznach (Bad Kreuznach) I have had great success using microfilm from the Family History Center in Salt Lake City. There are several film listed in their catalog for Parish records in Kreuznach. They cover the time period from early 1600's through 1798. You can rent these microfilm from the main library at any branch FHC. Go to familysearch.org to see the card catalog and to find the FHC nearest to where you live. If you need help in ordering, go to your branch FHC and they will help you.
I happen to have 3 or 4 film of Kreuznach Parish Records (Evangelical) on long term loan so I can access them whenever. I am not at home right now,so can't tell you what time periods they cover but I think it's a pretty big range. I will be at home by Sunday. If you want to e mail me at my personal address: - bhunt@mvdsl - I'll let you know what they are. Maybe I can help you get started. I'm sure you can follow Charlotte's parents back in these records; or others if they were Catholic or Reformed. If you think you can't read the records, don't worry! It only takes a little practice to pick out the names and dates. With time, and a German dictionary with genealogical terms, you'll be surprised at what you'll learn.
Hermann is also one of my ancestral names but they are from Wuerttemberg rather than the Rhineland.
Good Luck with your research and contact me if I can help.