VANCOUVER — Even if things had turned out differently, and Kelso had not tasted sweet revenge against Mountain View here Tuesday in the Southwest 4A District fastpitch championship game, the Lassies probably still would have made it to the prom on Saturday night.

“But,” pointed out junior Jenna DeRosier, “we would not have had time for dinner.”

Thanks to DeRosier’s masterful pitching, a clutch hit by junior Karina Paavola and superb team defense, Kelso moved within one win of the regional playoffs by beating the Thunder 3-1 at Heritage High School.

The Lassies earned a bi-district playoff berth and a home game along with the district title. A loss on Tuesday would have meant, at best, a playoff game in the Seattle area on Saturday.

Instead, Kelso (18-4) will host the KingCo Conference’s No. 4 seed at Lassie Beach — within eyesight of the Red Lion Hotel, site of the prom.

“We were a little stressed out about prom,” said DeRosier, who did not pitch in 3-2 and 2-0 Lassie losses to Mountain View during the regular season. “I’m just glad we won.”

Truth be told, prom logistics were way down on the list of reasons that Kelso was fired up before, during and after Tuesday’s impressive victory, which dealt the fourth-ranked Thunder (19-2) its first loss of the year against a GSHL 4A foe.

At the top of the list?

Pride.

“Coach asked us, if we could play one team for the district championship, who would it be?” DeRosier said. “We wanted to kick Mountain View’s butt.”

In the first two games between the Thunder and Lassies, Kelso imploded defensively and struggled to generate offense against Mountain View’s talented pitching tandem of Amanda Livingston and Kelly Lowe. The Lassies committed four errors in each game, Kelso coach Mike McMahon noted, and never played with a lead.

After a scoreless first inning on Tuesday, Kelso had trailed or been tied with Mountain View for all 15 innings of the three-game series.

Facing Livingston, the Lassies loaded the bases in the bottom of the second with a Crystal Nyman single, Brittany Sanders walk and Tailer Snow single. But Mackenzie Martin’s sharp grounder to shortstop was swallowed up and thrown home for a force out, and when Livingston bore down and struck out Mackenzie Southard, it appeared that Kelso might squander its best scoring opportunity of the season.

Paavola, batting ninth in the lineup, came to the plate.

“I was amped. We were all screaming,” DeRosier said. “Bases loaded, two outs.”

Paavola hit a home run against the Thunder earlier in the season, but approached her crucial at-bat with more humble aspirations.

“I was just working on getting a base hit,” she said.

Paavola nearly outdid herself, booming a deep fly ball to the base of the wall in right field that “would have been a grand slam if the wind hadn’t been blowing in,” McMahon said.

Paavola settled for a triple, with Sanders, Snow and Martin scoring in front of her for a 3-0 lead.

“It felt great,” Paavola said, “but we were due to beat them anyway.”

“Just a big relief there,” added DeRosier. “I knew we had it after that.”

There was plenty of work to do, yet. DeRosier had been overpowering to start the game, striking out five of the first six batters she faced.

With the lead, she relied more on her defense — with the timely strikeout sprinkled in for dramatic affect.

The biggest Mountain View threat kindled immediately, in the top of the third. A one-out double by Lowe and single by Jessica Guy put baserunners at first and third with one out. The Thunder sacrificed Guy to second, but DeRosier struck out three-hole batter Paige Martin to strand both runners.

Brittany Sanders made a nice play at third base to strand a runner in the top of the fourth, reaching up to grab a screaming line drive off the bat of Courtney Kelly for the third out. DeRosier robbed Martin of a base hit in the fifth when she stopped a sharply hit grounder headed for center field and threw to first for the out.

“We just weren’t intimidated today,” McMahon said. “We played tight in both (league) games this season, but not today. And what can I say about Jenna? She kept her focus and hit her targets. She really wanted this game, and it showed in her effort and in the results.”

Paavola spent the first half of the season batting in the middle of the order, but was stowed in the No. 9 spot as a secret weapon, McMahon added.

“She likes hitting ninth. Most girls don’t, but she does,” he said. “It surprises people, i.e. Mountain View.”

DeRosier took a shutout into the top of the seventh before the Thunder finally broke through. Kelly doubled leading off, was sacrificed to third and scored on a groundout by Lowe.

DeRosier coaxed a grounder to short by Guy, Mountain View’s dangerous leadoff hitter, and DeRosier’s cousin, Nyman, threw to first for the title-clinching out.

“We saw both of their pitchers this season, but they hadn’t seen me,” said DeRosier. “I’m really proud of us. We worked hard to get where we are. We deserve this.”