Naruto's Oka-san appearing is not unexpected since his father already appeared once. "However, what part of the tame the kyubi equation does she belong to is the question!

1. Suppresing of the evilness in kyubi?
2. ...

anyhow, the properties that the 5 element seal has been revealed far surpassed what we know. Its ability as a Hologram/virtual reality storage of a person memory makes me think of "nen" from hxh that in death a person's nen can become far more potent then when in life.

Also draws comparison to Harry Potter's Mother, who cast a protective spell on HP.