Examine these documents carefully:
New York Passenger Lists, 1820-1957 about Concetta Rosalia Siragusa
Name: Concetta Rosalia Siragusa
Arrival Date: 26 Oct 1928
Birth Year: abt 1869
Birth Location: Italy
Birth Location Other: selafani
Age: 59
Gender: Female
Ethnicity/Race/Nationality: Italian (South) (Italian)
Port of Departure: Naples, Italy
Port of Arrival: New York, New York
Ship Name: Conte Biancamano
Sheet 1, Line 2:

Sheet 2:

Border Crossings: From U.S. to Canada, 1908-1935 about Concetta Granata
Name: Concetta Granata
Age: 60
Estimated Birth Year: abt 1869
Arrival Port: Niagara Falls, Ontario
Date of Arrival: 13 Aug 1929
Birth Location: Sclafani, Italy
Gender: Female
Citizenship: Italian
Line 16:

The first is a passenger manifest for Concetta Rosalia Siragusa arriving in the US in October, 1928 from Sclafani. On sheet 2 of the manifest, we see that her husband's name is Vincenzo Feudale and that she is coming to visit her son Filippo in Brooklyn, crossed out and then Mario (?) written in.
The second item is a US-to-Canada Border Crossing some 10 months later in August, 1929, for Concetta Granata from Sclafani. The name of her husband, who is still in Italy, is "Vencinzenso" Feudale.
Clearly, both of these documents relate to the same person; it seems possible that she made the trip to Canada because her original visa was set to expire (page 2 of the manifest above). I am inclined to believe this might be the very same Rosalia listed residing with Mario in the 1930 census (taken on April 11, 1930). Of course, we would have to account for two things:
1) That "Concetta" returned from Canada in time for the April, 1930 census
2) Possibly Mario's father died and "Concetta Rosalia Siragusa" (maiden name?) remarried a man named Vincenzo Feudale. I am not certain how else to account for "Concetta Granata" and "Concetta Rosalia Siragusa" both being married to Vincenzo Feudale.