Psychosis is a blanket term for the experience of any kind of loss of contact with reality. This can include hallucinations, delusions and impaired insight. Psychotic breaks can be caused by a plethora of things including mental illness, sleep states, grief, sleep depravation, overuse of caffeine, extreme stress, various neurological disorders, medicines or use of almost any and every recreational drug.
Likelihood: VERY. I mean, she was living on a boat by herself. Just the loneliness of that alone may have caused her to imagine she was having sex with an otherworldly being. Not to mention what recreational substances might have been aboard. But who am I to judge what a lady does on her spirit journey?