PwBPD was confused by the very concept of what lying is

I had asked my pwBPD about a few cases where she was caught lying. She claims that even though she lied, even though she covered it up, even though she was caught red handed, even when her friend ADMITTED she covered it up for her, even though the lie was corroborated by such friend, she STILL didnt get that it was a lie. It's like she mentally doesnt understand the concept, thinking words are just things you say with no consequences. But if I lie about a tiny thing (ive lied about one thing in our entire relationship, and she flipped out).

What I lied about is that i didn't tell her about something that happened years prior to ever meeting her. It wasn't even relevant to her, had nothing to do with her, and i felt incredibly uncomfortable talking about it. My dad had passed away and she kept pushing questions about it, and I lied by claiming something he did that he didn't do. It wasn't even serious, it was incredibly stupid, I just didn't want to talk about it.

But we're not talking some amount of questions, it was a flood of questions and I hated talking about it. It didn't involve another woman during our relationship, she was prodding for answers on incredibly sensitive conversations. And even when being told to stop, she kept pushing on and on.