Board Thread:Speculation House/@comment-5414004-20141031064023/@comment-25555436-20141116174540

Or maybe...I think I'm onto another theory:

-Raven didn't go away, she ended up in another dimension. A dimension where time went slower, and with different laws than Remnant. That's why by Vol.2 she looks sooo damn young.

-She learned how to make those portals in that dimension. Which isn't teleporting, but going to that dimension, walking a few steps, and going out somewhere else. It's not semblance, but technology imitating nature.

-Taiyang, somehow, was able to see Raven momentarily at times when she was in the other dimension. He didn't know if it was real or not.

As for what dimension she went to, I say the 4th Dimension. Which is why no one was able to see her, but she could see everyone. A la Slender Man.