Frisk fell into the Underground, and the first monster found by her was Flowey. Flowey attempted to kill her, but got stopped by Toriel. Toriel guided her through The Ruins until Frisk wanted to go back to the Surface. Toriel attacked Frisk in order for Frisk to "Prove herself to her", and Frisk spared Toriel, and went through the gate.
Frisk encountered Flowey, and he mocked her.
Frisk is caring, never killing a monster in her endeavors.
Frisk has a kitchen knife (Much like Chara's) but doesn't use it, only more emergencies.