At Moama Recreation Reserve, Rochy scraped home with a single wicket to spare, breaking Mower hearts in the T20 fixture.
The visitor won the toss and opted to bowl first, sending Moama in to set a target.
It looked a good decision early on, as Mia Arthurson and Beatrix Bray departed without score, leaving the host in an early hole at 2-4.
Captain Delaney Laffy steadied the ship in a crucial innings, while Olivia Davy hung around to give her leader some stability.
Laffy would add 19 off 18 before departing and, while there were several starts down the order, only Jordan Dalziel reached double figures as Moama concluded its 20 overs at 7-97.
Alyssa Braithwaite, Hayley Broucek and Trinity Hayler shared the wicket-taking duties, picking up two each.
Broucek also proved useful at the top of the order, knocking around a measured 10 and providing a counterbalance to an aggressive Cadence Major in a game-defining second wicket partnership.
Meeting at 1-14, the two added 49, primarily through Major, who belted eight boundaries for 44 not our before retiring.
Broucek had retired earlier and their separation sparked a collapse from the Rochy batting order.
At one point 1-79, the middle and lower order capitulated to 8-95, forcing Broucek to be recalled, and with the scores tied, Major also returned to hit the winning single and ice the game.
Laffy matched her batting effort with the ball, taking 3-9, while Madilyn Van Poeteren and Olivia Davy took two apiece.
Echuca had the bye in round four, while other results saw Nathalia top Katamatite by 20 runs and Bamawm-Lockington United take down Cooma by 48 runs.
The competition now moves into one-day, 35-over fixtures with Moama travelling to Katamatite, Nathalia hosting Cooma and Echuca welcoming BLU to its temporary home of Tongala Recreation Reserve.
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