Not a thought of that. Your theory (or at least something similar) would certainly apply to be exBFF. We used to see each almost every day, even if only briefly. We even went on holiday together. We treated each other like family.
The only problem I ever had with her was her politics. I am left-ish. She is right and these days far right. I n the latter years of our friendship, she was constantly bringing up topics that I didn't agree with her on. Sometime, I just wouldn't say anything and sometimes I would tell her why I disagreed, which she always got very cross about. So she still believes the MMR causes autism and took no notice when I told her it had been disproven. In fact she is anti vaccines in general and advised people not to have them (and some listen). She doesn't believe climate change is an issue or at least thinks it's vastly exaggerated. She thinks that 'England is no England' due to immigration even though both of her parents are immigrants and barely speak English etc etc etc. I think it is perfectly possible to be friends with somebody who has views which I consider to be ridiculous.
Anyway, I spent years discussing DPs bad behaviour with her . She was always very understanding about that and gave me a lot of advice advice - some of it excellent, some less so.
Eventually I came to the point when I realized DP was actually an abuser and narcissist, my DCs were very young adults and I decided it was time to leave DP. When I told BFF where I was moving to (a flat), she told me that my new home was infamous locally for drug dealing and prostitution. This was after I paid the deposit. She told me it was dangerous and I would be woken up at night by police raids and would be stepping in vomit in the corridors. I spent about two nights tossing and turning, worrying that I had made a massive mistake. Anyway, moving day came and about a week later, I was chatting to a group of neighbours who had all lived there for 15 or 20 years. I told them what BFF had told me and they didn't have a clue what she was talking about. That made me realize that she had made the whole story up.
I then messaged her and told her what my neighbours had said and how long they had lived there. I was obviously indicating indirectly that I knew she had lied. She then sent me a lengthy email saying that she was upset that I didn't know that she was trying to protect me and anyway I didn't agree with her on anything and she tired or arguing with me.
Nobody protects their friends by telling whooping lies like that!!!
In retrospect she was a narcissist too. I think she didn't like me moving away (we lived in the same road). She obviously should have just apologised and that would have been the end of the matter.