Blaze does not come from another dimension, she simply comes from another island. Either Boomiverse Southern Island but I don't see reason why writers would bothe rnaming it, just like the name of Bygone Island is never mentioned in the TV show.
She is not guardian of the seven Sol Emeralds, instead her duties is guardian of the Sun Crystal, one of the eight (or perhaps many more) Chaos Crystals.
Still just an idea. Nothing is actually confirmed.
If only I could remember where that thread was. Was it in General or Boom board?
Well, when Season 1 began, Bill Freiberger said there will not be any other characters other than Metal Sonic and Shadow. However the thread I'm looking for says he would reconsider this for the future of the series.