There is that "privacy issue" for Elizabeth - Alzbeta. You would need to hire a researcher to try to find her. If the parents were married in Bohemia than she too would have been born in one of the locations that you have for her parents.
Have you considered or tried: https://www.facebook.com/CzechoslovakiaGenealogy?ref=hl
Might you consider sending a letter of inquiry to the HELFERTs that are in CZ's phone book?