The 13-goal win keeps the Lions in eighth spot on the Kyabram District League netball ladder, four points behind Shepparton East and Merrigum.
But Amanda Gledhill's side was made to earn their win against the Redskirts.
"We started quite slow, but Longwood's attacking end was on fire," Gledhill said.
"They brought the pressure to us.
"But I was proud of the girls' efforts to grind out the win under such high pressure.
"It was a really important game for us to keep our season alive."
The 14th-placed Redskirts brought their A-game to Undera Recreation Reserve, making life difficult for the Lions.
Undera had a small lead at the main break, which Gledhill said they used to focus on two areas of their game.
"We always held a lead throughout the game, but Longwood cut that down to two or three at the half," she said.
"We spoke about slowing the ball down and just getting back to basics."
The Lions came out roaring after the break and powered ahead thanks to Amy Reid in goals and defensive pair Jaidyn Mitchell and Katie Dorsett.
"Amy played a strong game in attack and both Katie and Jaidyn were solid down back as well," Gledhill said.
"They're both really skilful players and they changed the momentum of the match with their ability to intercept the ball."
The Lions have a bye this weekend before returning and fronting up against undefeated Stanhope.
DOT POINT: In other results, Rushworth clinched a dominant 74-17 win against Ardmona.
Nagambie was too strong for Lancaster, securing a 48-20 win.
Shepparton East remains level on points with Merrigum after defeating Girgarre 39-31.
Merrigum kept its finals aspirations alive with success against Avenel, while Tallygaroopna powered past Violet Town 62-19.
Stanhope stormed past Murchison-Toolamba 85-38 to complete the round.
SCORES
Undera 46 d Longwood 33
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