Hey

What is your proof on Mari/Nao? Another thing is that Nao never forgets the player, that means she is not a Tuatha Danann. And I'll fix that Error. They can only Enter Erinn's Soul Stream when in Erinn. Let me make a map to show what I mean. I'll update this post in a moment.

UPDATE:

This is basically how the worlds work. Erinn's Soul Stream is where Nao is. Erinn Soul Stream acts as a gateway between Erinn and other Soul Streams. Glas/Dougal was summoned to Tir Na Nog while he was in another world. Tir Na Nog is connected to Erinn, but not directly connected any Soul Stream. Therefore, he would have to first travel to Erinn to enter Erinn's Soul Stream without otherwise being summoned.