Dual personality?

Dissociative Identity disorder.

My best friend and I had a lengthy discussion about this particular topic, ten hours ago. She told me about her ex-boyfriend having a split personality, according to him. Space Ed. I understand why she wouldn't believe him, her ex-boyfriend ended up being the embodiment of a liar, but she told me anyways, of the first time she met 'Space Ed'. How even the guy's facial expressions changed. He had on this smile that so unknown to her, and a laugh that sent chills down her spine and a look in his eyes. With a deeper voice, 'Space Ed' spoke to her, telling her much he hated her, hated the boyfriend and even more hated how they were together. He swore that he'll end the relationship, he even came around her and choked her. She was crying, shouting her boyfriend's name, and when he came back out, he couldn't remember anything that went down.

Now some people will argue that it could just have been him showing his true colors, by blaming it all on someone else.

I actually have a theory, and it doesn't apply to DID, completely, because I, personally believe in it. My theory is that, because of society, and rules, and how we are brought up. We can disown the traits of our personality that we do not approve of, and in doing so, we create a split personality, because of course, the traits are still there, but you tame them. How many serial killers go about their daily lives, smiling to everyone, being all good and then, we have that hidden secret in the basement.

How many times do we see child molesters and hear the comments "I can't believe he'd do such a thing, he was such a sweet heart, always helping everyone" You could be the nicest person on earth, but that doesn't mean you don't have that little trait in you that can change all that in a split second.

The last time my best friend encountered 'Space Ed', he had laughed at her and told her that he was the cause of the breakup, that he was happy it was over and how he doesn't like 'the bitch he's dating now, either' and soon he'll end that as well. Once again, just having him near her, sent chills down her spine.

If my theory applied, it would mean that the ex-boyfriend brings out the most sadistic side of him, when he's 'Space Ed', but believing in DID, 'Space Ed' is an entirely different being, stored away in the depths of his being, and in that moment, he's the dominant one.

But, the real point to this isn't to breakdown whether 'Space Ed' is real or not.
I want your thoughts on this whole ordeal. My best friend argued with me, that although, the encounter made her want to believe in it, she also completely denies the existence of that disorder. She believes that it's people using the excuse of a 'second being inside of them' to show their true animalistic side.

Because, as she has stated, we live in a world that had been pushing down our throats what is right and what is wrong, we have morals and rules and punishments. So, many people look for excuses to misbehave. (It's like saying "I can be a bitch to you, because I'm a Leo and that's just our personality trait" You're just blaming your bitchiness on the fact that you were born between the days of July 22nd to August 22nd)

I agree with her, but I also believe that said disorder does exist, especially after hearing her breakup story. I knew the boyfriend very well, and although I always said it will end badly between them, I never expected all of that. I never expected for him to sit next to her, watch her cry and not feel guilty, and not call off everything that was going on.

She said it herself "I still can't comprehend how the same person who called me 'baby, sweetie, mi gordita, my love...' could turn around and call me 'slut, whore', and so many of the other awful things"

So,I'll finish with, I want to know your view on this, on multiple personalities?
I want to know what you think on my best friend's view on it?

(I have a really awful way of explaining things and getting to the actual point, so I hope there's no misunderstanding)