DEEP SPOILER WARNING!
This page contains major spoilers for the plot of Broken Minds.
Noa's motive seems simple at first. She wants friends. And Dr. Uzumaki believes that your parents get in the way of you making friends. Therefore, she killed her parents and tried to befriend everyone she met because of it: Ume, Takuma, Yuzuki, and Reiwa. However, she was turned down every time. Ume was just playing along. Takuma was pretending to want her in the YPDA just to see if she would slip up and reveal herself to be the killer. Yuzuki was more concerned about her hair than Noa's plight. Reiwa turned Noa's offer of friendship down because she "found her annoying".
Unlocking the persona stories reveals why Noa isn't able to make friends in the first place.
Nice Noa talks about making a new friend when she was younger, named Etsuko. However, in Liar Noa's story, she plans on playing a cruel prank on Etsuko. However, as is indicated by Puppet Noa's story, she is pushed to do it by Liar Noa. Liar is manipulative and never gets her hands dirty, always choosing to force Puppet to do it.
Noa's "evil" states (Psychopath, Puppet, Liar) always ruin Noa's friendships, but because they're all part of Noa, and Noa deeply wants to make friends, the goal of the "evil" states is also to make friends, just in a more horrible way than the "good" states.