Gymns became the final team to qualify for the Warehouse Fitness Floodlit Cup semi-finals on Sunday.
A goal in each half from Kayleigh Whitehead booked their place at the expense of Colby in a 2-1 win.
The southerners, who only needed a draw to qualify, replied through debutant Sarah Wignall.
TT 2026: Three races due to take place today
Supersport, Sportsbike and Senior Races all on the schedule
Southern 100 planning to run classic sidecars for 2026
It's after modern machines were excluded from July event
Glover - Southern 100 sidecar suspension felt 'completely inevitable'
Former commentator believes work to help class needs to start soon
Football: Freddie O'Donoghue released by Carlisle United
Manxman had been with Cumbrian club since 2023
Southern 100 sidecar exclusion 'absolutely devastating'
Competitors react to class's removal from Billown Course for 2026