Kristi,
I hope one of the list members can help guide you on your quest.
This Banat group primarily focuses on The Danube Swabians (German: Donauschwaben) - a collective term for the ethnic German-speaking population who lived in Kingdom of Hungary of east-central Europe. This area is now Romania and Serbia. See link.
Hesse-Darmstadt is located in Germany ... not Romania or Serbia.
What is your Great Great grandmother's name and date of birth? When do you think she arrived in the USA?
Wayne