Often, alien encounters can be linked to some kind of traumatic event in a person's life. It could be that the trauma is too much for the mind to process, so it invents something to fill in the gaps.
A Reddit user that has since deleted their account recalls their mother's story:
When my mom and Lisa were teenagers, they were up on the roof of Lisa's house, and they see a bright light in the sky. Next thing they know, the light is gone. Thing is, they think they've been on the roof for like 15 minutes, but something like 3 hours passed.
So a couple months later, mom moves away and loses contact with Lisa for about 10 years. She finally meets up with her again and immediately notices that something is odd about Lisa.
Lisa appeared very "distant" to her, with a very "dreamy" demeanor. Like she was really happy and at peace, for no good reason. After they talk for a bit, Lisa brings up the incident on the roof.
At first, they paralyzed her somehow and did all sorts of invasive experiments on her, but by the most recent time, they stopped probing her and began to talk with her. [...] Apparently they told her all sorts of things - stuff about space, Earth itself, and most shockingly, predicted years beforehand that she would get pregnant in a specific year and it would also be a stillborn, and that she would never be able to have children again. They also told her that it was not their fault and they even made an attempt to save her from this fate, but they were unsuccessful.
A psychologist might conclude that "Lisa's" experience with the aliens is her brain's way of rationalizing an incredibly traumatic experience,perhaps even prescribing meaning to it, and helping her deal with it.