How can you find her mother's maiden name?
Most logical place to look is on Canadian documents, ie Marriage Certificate, Her childrens birth certificates, Obituary or Death Certificate or any Canadian government document that would require such info.
Other than this you would need to determine which one of the numerous Haselbach was her hometown in Austria.
I've attached the ship manifest to this message, which gives her destination as Winnipeg, Manitoba. She is on Line 4
In addition the next year, 1929, Alois CHRISTL from Haselbach, next of kin Rudolf CHRISTL arrives in Canada, Destination ? He is line 1 on the second manifest attched to this message.