Robin, I took a look at all of the merged-away profiles to try and figure out where the error could have been. In all cases, they appeared to represent the same person. According to the change logs, following is their information at the time of their creation. Some of them went through other changes after that, before they were merged into Katzenberg-1, but after reviewing their changes, there isn't anything to suggest they shouldn't have been merged.
- Katzenberg-1, Marguerite Katzenberg, created 03 Nov 2011, born 10 May 1751 in La. [later edited to be 09 May 1751 in Germany], died 1794 in La. [later edited to 1795]
- Katzenberg-2, Marguerite Katzenberg, created 03 Nov 2011, born 10 May 1751 in La., died 1794 in La.
- Katzenberger-55, Marguerite Katzenberger, created 25 Apr 2015, born 1751 in La., died 1790 in La.
- Katzenberger-62, Margarete Katzenberger, created 09 Jun 2016, born 1751 in La., died 1795 in La.
I don't know where or how your ancestor's profile would have gotten mixed in with these profiles. I found nothing in the change logs about another Marguerite Katzenberg/Katzenberger getting merged in to this group. It's a mystery. But regardless, since a merge can't be undone as someone else has said, about the only suggestion I can make for your missing ancestor is to create a new profile for her, making sure to include as much information as you know or can reasonably estimate, so that she doesn't get accidentally confused again, and link her to the appropriate branch of your tree.
I hope that helps, and so sorry for your frustration.