I have been working on a post-apocalyptic novel for about a year. My female narrator/protagonist, named Eris, was isolated for almost all of her life until meeting a rogue group of survivors and having to assimilate into their world. It's the year 2212 and this world was devastated by decades of nuclear war, leaving a majority of the Earth polluted and radiated, which subsequently modified the human genome and gave many people strange and unexplainable abilities.
Eris had convinced herself that she was the last person on Earth until the group of survivors picked her up, and while she does the possess uncontrollable and "supernatural" ability to manipulate life force, she is not only hiding this from her new companions, she has convinced HERSELF that this power does not exist and blocked out its usage from her mind, and this blockage of memories inadvertently manifests in odd nightmares and premonitions (when she was a girl, she lashed out and accidentally killed her father, aunt, and older sister, and when this commotion was investigated by other survivors, she murdered them out of fear).
She not only is lying constantly to those around her, but even when she is alone she is unable to acknowledge the truth of her actions because they were extremely traumatizing and she harbors extreme guilt. She also misunderstands body language, does not realize the effects of her own actions and lies about them to herself resulting in inaccurate narration/retelling of the events, and frequently gets so caught up in her own emotions that she blocks out what is happening around her.
My question is: how can I convey her inner conflict and inability to trust herself in an effective way? I don't simply want her to tell lie after lie, but I want her to build a sort of inability to both tell the truth, identify whether what she is saying IS the truth. The suppression of her powers and guilt about using them is a big reason for her unreliability and motivation behind her lies and manipulation. She isn't necessarily a sympathetic character and I don't need/want her to be, and I don't want her to learn how to tell the truth or develop morals; my main goal for her is to be a destructive person and a bad source of information.