In her perspective, she’s trying to save her children from the end of the world. To everyone else, she’s killing her daughters. She took a knife and slit her daugheters writsts and throat then did the same thing to herself. Luckily her friend arrived unexpectedly early. Called 911 and they reached them in time before anyone died. You can see the wound in her mugshot.
I’ve taken the fact that the world ends today very comically. I would have never guessed someone would take this extremely seriously though. It doesn’t even make sense to kill your daughter if you believe everyone’s going to die today anyway.