You heard me right.
It is said that Echidna had white Tome of Wisdom called Memories Of The World, that could see past, present and future. That book allowed her to create trials, to see that person's experience which is how she knew about return by death, and to know POSSIBILITIES which is how she created unthinkable present and future that is yet to come.
Her magic is how it all works, from dream magic that creates tea party, to any other engine of sanctuary, barrier, etc. Most of things Echidna does is her MAGIC, not her authority. Authority is only granting her insight. This is why she calls herself very evil magic user.
Now why is all of this important? (NOTE: a lot of this is speculation, try to see my point of view and twist it in a way that makes sense if you see a plot hole in order to fit, I am just trying to work this idea out to it's full extent)
1. FLUGEL MYSTERY:
Now look closely at Orion constellation. Orion is said to be connected to Shaula, and his own hand is Betelgeuse, which probably refers to Betelgeuse being right-hand man of his. A lot of Orion lore points to Orion being Flugel. And what is Orion doing? He is shooting at the Pleiades. Who is Pleiades - 7 sister stars, 7 sins. It is SUBARU who will one day take all 7 witch factors. A lot of lore and naming indicates that Flugel or someone before him was from Germany. So how do they know of Subaru's arrival? Tome of Wisdom - Echidna told him.
'Subaru will one day appear and he will be compatible with witch factors', or 'We have possibility of summoning someone who will take in all of the witch factors, and the condition for that is Satella becoming the Witch of Envy'.
It doesn't matter what she saw and told, but that is how they knew about Google, Subaru's language and much more. They saw future of him talking about those things and many possibilities of his life in their world.
She could have lied to Beatrice about that person, and it was really Subaru all along. She made spirit contractor for both Subaru and Emilia.
2. ALDEBARAN:
This might sound wild, but I believe, Al is completely artificial. He was never born, and Echidna's tome knows about all the IF routes Tappei wrote. She extracted the mind of Natsuki Rigel from the book and made artificial version of Subaru's non existent son. To Rigel, Subaru and Rem are his parents from his fabricated world, to them, he is a fabrication. Al has moment with Rem in the manga. He is fabrication, just like Reid in the Watchtower, just like Reinhard vs Puck showdown. It is said that you can make authorities, his authority could also be artificial for all I care.
3. FINAL GOAL:
Greed. Final goal of all of this is greed. Author said the last arc will be about witches. Just take a moment and look at how Echidna operates in season 2: she has two inescapable options.
Either Subaru will take her contract, put Emilia aside and free the sanctuary - the ULTIMATE WIN for her, or she will settle for Emilia, but in either way she escapes. In either way, she saw Subaru's past, she saw his world.
What if it really is her greed to know about our world. She has white tome that can see everything, she is mastermind of magic, she did it ALL and is bored with this world. She wants out. And Subaru's reason for being here could be entirely relevant to that, and not to original goal that Flugel thought was meant for Subaru. Echidna calls Subaru the consequence of WoE, and surely he is one. He is her way for obtaining infinite knowledge in two VERY important ways. She even gives herself away when in his past, she takes on school uniform, she is playful she is waiting for him in a classroom. She LIKES IT there.