Who would be dominant?

Jessica • I`m pretty much just an adult version of Mabel Pines
If someone has another personality and the personality that everyone thinks is the "original" personality is not aware of the existence of the other personality and the other is very well aware of everything of the "original" like memories from years and years ago and personal information plus this other personality is self aware like it knows it's technically not real (it's real in the mind but not a physical entity) and does not possess its own life would that make the aware personality the dominant one?