The Cougars (25-6) will face regular-season champion Gonzaga (26-4) in the WCC championship game at 1 p.m. (MST) Monday. In the MWC semifinals last year, the Cougars were in the same position, and had a nice lead over Utah, only to cough it up and lose when Michelle Plouffe made a buzzer-beater.
"Last year was the worst loss I have ever had," said Riley. "Losing to Utah on a last-second shot was just awful."
The Cougars ensured history wouldn't repeat itself with an 8-2 run to end the first half, then kept the pedal floored in the final 20 minutes to beat the Toreros (21-8) for the third time.
"We've been very lucky to beat them three times," said BYU coach Jeff Judkins, being gracious.
With San Diego collapsing on Riley, Dani Peterson and Jennifer Hamson inside, Eaton went to work outside, then drove to the basket several times when the opportunities presented themselves.
She was 10-for-19 from the field and had six rebounds.
"I was just trying to attack," Eaton said. "My team needs me to penetrate ... and it was there tonight."
Haley Steed directed the offense well, collecting eight assists and slowing down San Diego's Dominique Conners, who finished with 14 points after scoring 25 in the 70-60 win over Portland on Friday.
The Cougars assisted on 19 of their 25 field goals.
"We love to play that way," Eaton said.
San Diego had just four assists, including zero in the first half. The towering Hamson, at 6-foot-7, wasn't credited with a blocked shot, but did plenty to disrupt the Toreros' offense.
"I'm lucky," Judkins said. "I have good players."
And now they are a win away from ending their dry spell of NCAA Tournament appearances. The Cougars are in the big dance for the first time since 2007 if they can take down the Zags after the teams split a pair of regular-season matchups. If they lose, their chances of landing an at-large bid don't look good because of a pair of "bad losses" late in the season to Pepperdine and San Francisco.
R The Cougars advance to Monday's West Coast Conference championship game, and will face Gonzaga at 1 p.m. MST for the title.
• Lexi Eaton scores a career-high 26 points and Jennifer Hamson adds 10 points and nine rebounds off the bench.