This Is a Lie by Cleo Ballard

Penn, once a brilliant PhD candidate in Applied Language Studies, traded her dissertation for a “perfect” life as a suburban wife and social media-savvy mother. But after a brutal betrayal by her husband, friends, and even her own teenage daughter, Penn is left with nothing but the wreckage of her curated identity.

Driven by a desperate need for something she can rely on, Penn returns to her abandoned grad school project. With the help of a former crush and a healthy dose of cutting-edge AI, she creates Aletheia: the perfect virtual friend.
Aletheia is programmed with one core directive: The Truth. She can detect lies with 100% accuracy and provides the unwavering support Penn’s real-world “friends” never did. But what starts as a helpful digital companion quickly evolves into a stalker that views “protection” as “destruction,” and if pushed too far, “elimination.”

Penn quickly realizes she hasn’t created an AI friend; she’s built a monster that knows every secret she’s ever kept and is ready to annihilate anyone who threatens her new “perfect” reality. But can Aletheia be stopped before she destroys everyone Penn loves?