Geitz herself was close to best on court - finishing with a game-high five deflections defending in combination with Clare McMeniman and Rebecca Bulley.
Underlining their status as the best defensive unit in the competition, the Firebirds held the Swifts to just 18 goals across the third and fourth quarters.
Coach Roselee Jencke said the side would gain confidence from the win in front of a 5,175-strong home crowd at the Boondall Entertainment Centre.
"To be able to finish off they we did was excellent, to now get a home semi-final with our crowd and just how loud they were is fantastic," she said.
The Firebirds will host the loser of Monday's New Zealand conference final between Northern Mystics and Waikato Magic for a place in the grand final on June 21.
Seemingly showing no ill-effects of Friday's extra-time victory over West Coast Fever, the Swifts took a 13-10 lead at the first break and increased their margin to six goals early in the second.
However, a 17-13 second quarter saw the Firebirds take a 27-26 halftime lead.
The Swifts must now regroup for an away clash against the winner of the NZ conference final.
- AAP