Meike Meilleur paced the Flames attack by scoring the game’s first two goals in the opening period and adding an assist in second.
Randi Marcon and Christian Higham also tallied for St. Mary’s.
Bailey Chenier suffered the setback in net for Thunder Bay.
Next up for the Sportop Queens will see them heading to St. Paul, Minn., Nov. 28-30 to compete in the Minnesota Mayhem tournament.
Meanwhile the midget A Queens were also blanked by a team from Winnipeg Sunday as they fell 1-0 to the Manitoba Silvertips in the semifinal of the Confederation College Caribou Classic at Fort William First Nation Arena.
That contest was scoreless well into the third period before the Silvertips’ Taylor Boehlig notched the only goal of the game with eight minutes remaining in regulation by the slipping the puck past Thunder Bay netminder Cameron Ivall.
The result meant it was an all-Winnipeg final as the Northern Stars from the Manitoba capital edged the Con College Thunderhawks 2-1 in overtime in the other semifinal of the inaugural Caribou Classic.
Next up for the midget A Queens has them heading to Buffalo, N.Y., next weekend to take part in the first-ever Harbor Center Cup Nov. 21-23.