They once were all one, a mage triying to discover how to ascend to another plane that ended up shattering themselves in mind, soul and body. She is the soul, and funny enough was the second one to wake up, only moments before Mind.
The Dream Traveler
Somewhere along the path she realized that more than dreams, those were realities she was visiting, and once became lucid with the fact she could bring her power with her. The spell the mage made may have gotten out of control but some part of it worked after all. With time she started to create her own, what happens to them once she wakes up? She also wishes to know.
Soulmates
She is not the only one as she is only one of three. As far as she knows (which isn't a lot) she can go to other realities, Ren dictates where and modifies the worlds she makes and Neo is their ankle to reality.