That's a tad too convoluted, don't ye think? Before long we'll also be lead to believe that both of them are actually the reincarnation of two mighty spirits that stood on opposite grounds within the wells of karma.
I think it's much more feasible to assume, that because the girl was never wronged or harmed, she simply doesn't have the concept that people are capable of malicious intent. From her perspective, surely, humans are only capable of being nice to each other. So she fits whatever she's hearing from the MC into that narrative.
