My cousin married into this Berta family (John) and the info I have is that Mary died in Feb 1925 in Johnstown and has an obit in the newspaper there for 28 Feb 1925. She is listed incorrectly as Mary "Borta" in the obit index. You can contact the Cambria Co. Library and for abt $5 they'll send you the obit.
Cambria County Library
248 Main Street
Johnstown, PA 15901
Phone: 814-536-5131
ATTN: Reference Dept.
This website has an index of burials & marriages in Cambria Co.(Andrew & Mary appear in the marriages for 1906):
http://www.camgenpa.com/
She is probably buried in one of the Catholic or Byzantine Catholic cemeteries there, depending on her religion.