Unless it was Preservation influencing Vin's mother.
I don't know how that works with the earring thing though, but it's definately something to think about. Either Ruin and PReservation can see the future, which I think is unlikely, how could they be beat? or the can cause people to have visions of the future
I wonder what else Vin's mother "babbled" about.
Perhaps, Vin's mother was able to use Atium, enhance by Hemalurgy, to se very far into the future? But she wasn;t msitborn so that doesn't work. I don' think it's a coincidence though that there are metals that let someone see the past and the future, and Vin;s mother is babbling things that actually happen later one.
It could be she was just proclaiming Vin the hero of ages because Ruin told her to: Terris philosphers claim Alendi is hero by giving him piercings, Vin's mom proclaims her a Queen, and gives her a piercing.
It was Vin's mother's own earring though, so what's the significance of that, since she is a hemalurgist it was probably already used, and maybe the baby sister was only used to transfer it's power.
Or maybe the earring has been passed through Generation, and it is the cage that holds Preservaiton