I'm not related and it sounds like you have already looked at the 1920 and 1930 censuses and found her parents.
The 1930 census of Perry Twp., Fayette County, PA:
Charles Zubak 38, born Czechoslovakia, immigrated in 1913 Julia 37, born Czechoslovakia, immigrated in 1913 Margaret 14 Charles 12 Helen 4 7/12 John 4 7/12 Irene 2/12
The 1920 census of Carroll Twp., Washington County, PA:
Charles Zubek 27, born Hungary, immigrated in 1913 Julia 25, born in Hungary, immigrated in 1913 Margaret 4 2/12 Charles 2 1/12
I could not find a Sophie or Nick Zobek or any similar spelling anywhere, but they may have been born after 1930.
Check with the California Area Historical Society to see if they can help you. You might also try to find Margaret's marriage record. The problem is in knowing where they got the license. In Pennsylvania they are recorded at the Register of Wills office in the county the license was gotten.