DRV3 spoilers here.

Kirumi at first said to Kokichi and Gonta;

"I shall take that request to be your mother."

Kirumi soon mothers both if them as we see when Kokichi tricks Gonta to kidnap them.

Kokichi was chased down by Kirumi while trying to mother Kokichi and discipline him.

Later, Kirumi kisses Ryoma to escape, knowing everyone else will get executed if she succeeds.

Basically, Kirumi took the task of being a mom and then was willing to kill her new sons.

She was going to let Gonta and Kokichi, her sons, DIE.

And we all call her a "mother Kirumi" like she's Toriel. BRUH TORIEL WAS WILLING TO DIE TO SEE IF FRISK, THE CHILD MAIN CHARACTER, HAD TO WILL TO SURVIVE. She was giving us butterscotch cinnamon pie for crying out loud!