Sandra de los Santos powered her way to a game-high 16 points while Honey Rose Tubino added 12 more.
The Rising Suns, who ended the preliminary round with a 7-3 record, will face No.2 Philippine Army Wednesday in a best-of-three semifinals series.
Cagayan beat Army split their elimination round meeting with the Rising Suns coming out on top in their recent match in four sets.
The Lady Eagles, who played without their key players Fille Cainglet and Alyssa Valdez, will have their hands full anew with league-leader Sandugo-San Sebastian in the other semis date.
Gretchen Ho had 13 points but had few support as Ateneo lacked the firepower to match up with the loaded Perpetual Help.