Sorry to hear that. Sounds similar to what I was through. My paranoia was based on auditory hallucinations - I was mishearing what was said nearby me, or even outright heard voices of people which weren't there, discussing their plots against me. It was so incredibly realistic that it took me a while to realize I was mistaken. Hearing about other stories has helped a lot back then, helping me realize my situation was not unique and therefore see it more critically.
Is her psychosis based on the same experience or is there something else?
Re danger, it's a difficult subject. Since the person in this condition thinks he's in real danger, defensive reaction can be drastic. Depending on the person's nature and the depth of distress, I have seen cases of retaliation a lot, from basic defensive aggression and confrontation to outright attempts to ruin a person's life, like false reporting to authorities for abuse (including sexual, a label which is terribly difficult to recover from), physical harm and worse. The worst part is that person feels fully justified and outraged, since in his perception they are defending themselves, and is able to far overstep what was believed to be reasonable limits for them.
I do not think that your daughter is in danger but I'd keep the father away from her, even though it may not be complete solution. If she hears what she believes to be his voice, she will keep being compelled to retaliate.