Well, a couple things. First off I don’t think the Dom/Daddy role needs to be pervasive in all aspects of a relationship for their intimacy to be D/s. Not everyone wants to have the chores, structure, discipline, etc, which is totally fine by the way. I assume that he doesn’t, and that is why he doesn’t want to have labels in his relationship, which makes sense. None of the first part of your Ask I see as wrong.
Now the part where he plays on her previous bad relationships – that is something totally different. People do this shit all the time and it is really unnerving to see. Girls do it too. The truth is, when you put time and your heart into a relationship, if the person on the receiving end of your vulnerability shits on you, it more often than not leave some scars. Personally, my first love did damage to me by always gaslighting me, playing head games and needing for attention elsewhere then making me feel crazy for bringing it up when she was clearly all over other guys, even though she wasn’t technically cheating. It took awhile to trust someone again without suspicion.
Being with somebody who takes advantage of your prior scars is without a doubt – a total douchebag.
My hunch is, you as her friend probably have a better perspective than she does about the quality of this guy, because when you are in the middle of things like that, losing perspective is part of the problem. Keep voicing your opinion because one day he will cross a line and she will see him for who he is, and she will be done with him. Right now she might just not feel like she has a good reason to leave, however not being loved is all you need.
But just because he doesn’t want to be a Daddy or a Master, doesn’t make him bad. Everyone deserves to have their own kinks and maybe he likes rough sex and is a kinkster, but is not into being a D/s figurehead in their relationship.