a. Try searching the Arolsen Archives for your grandmother's sister name:
https://arolsen-archives.org/en/search-explore/search-online-archive/
b. Try searching the Yad Vashem Pages of Testimony (PoT) database for her name as a testimony submitter (use the Advanced Search tool):
https://yvng.yadvashem.org/advanced-search.html?language=en 

Ilan Ganot
Holon, Israel
MMWS co-webmaster
https://kehilalinks.jewishgen.org/Mazeikiai/introduction.html