Dealing with Paranoids

I recently ended a relationship with my partner who has PPD. I tried so hard to understand but the constant accusations of being unfaithful, constantly bringing up perceived slights months and years later. It was a constant battle and i wanted us to work it out so much because i love loved her so much. Everyone has a breaking point. I never knew she had ppd until a few months after we broke up and then everything made sense. I have a few questions if someone has any answers. Is contant lying about things a symptom? Or is that just who she is? Do people with ppd accept they have it and understand their doubts are not justified or are they in total denial? Surely if someone has ppd and they love someone very much they would be able to trust in that person to be there for them. If they are convinced that their partner has been unfaithful would that make them rationalise being unfaithful in return? Or are paranoids generally loyal or maybe everyone is different? Our breakup hurt me very much because she just wouldnt trust me even though ipshe says i am the love of her life. Its confusing but reading this forum has certainly helped my understanding