Episode 1: Without her power and under Wanda’s spell, Agatha can still sense magical activities. And she is quick on action too.

1. Wanda’s death and the Darkhold.

The fight at Mount Wundagore would probably only known between Kamar-Taj and S.W.O.R.D (I don’t know what agency is still standing now, I don’t watch much); because quite frankly, that kind of news (witches/sorcerers exist, universe traveling, etc.) is not something you just drop to the public population. I suspect that Strange and Wong might not even disclose that information to non-magical users. So how could Agnes know? Remember that when Herb said “Oh, she’s really, most sincerely dead”, it’s from Agatha’s pov, while under Nosy Spell. And after Agatha wakes up, Westview people are still afraid of even speaking Wanda's name.

Wanda destroyed all copies of the Darkhold from every universe. Again, Strange and Wong might let others know that Wanda is dead, but there’s no need to go around and PR the (past) existence of Darkhold, because god knows what will happen. So how could Agnes know?

2. Billy being a witch.

Preferred when she “interrogates” him, there is a spelled dialogue “It’s ink from the fingerprinting” from “Teen”. Like I said in a previous post, her subconscious mind knows he is a witch, or warning her more like, because Agatha lives and survives by killing witches, of course she will learn to notice who is a witch.

3. The talk with Herb.

The moment she wakes up, she appears angry while asking Herb for information, but as Herb seems confused, she quickly changes the way of talking to fit Herb’s “sheep” mind and gets information she wants (aka she doesn't want to waste time on explaining her situation).

4. Rio’s domestic banter, aka literally playing with Death.

Now we know Rio is Death, we should all agree that if she wants Agatha dead, she could do it with Agnes. “You can’t kill me. It’s not allowed.” - This could be a seed for future reveal, or it could mean Death can’t go around, actively killing people. She’s a guide to the afterlife, not a killer. So Rio’s visit is a rescue and warning mission. This is the result of Rio visiting:

It’s Rio’s power that breaks through Nosy Spell after Billy loosen it.

Agatha knows the Salem Seven is coming for her ass.

My conclusion is, subconsciously, Agatha still has her sense when it comes to magical activities, which is honed after years and years of practicing magic. Or, the Nosy Spell using Agatha’s memories and sense to fill in her world, much like how the Hex environment and people are based on Wanda’s memories of those old tv shows, changed and reflexed by Wanda’s emotions; and because it based on Agatha’s sense and memories, the moment Wanda died and the Darkhold is destroyed, Agnes’s reality changed to fit with her sense, aka she knows what happened.

Episode 2: Agatha’s detective and manipulation skill at work.

1. The talk with “Teen” - She knows Billy is lying or hiding something from this exact talk.

From how Lilia and Jen behave, it's common knowledge to avoid Agatha Harkness - the witch's killer, if you want to stay alive. So what is wrong with this kid? If he knows “an egregious amount” about her, he should have stayed away. Does he have a death wish?

“If you’ve got the goods to break a spell cast by Scarlet Witch” - same point from my previous post. Why has no one tried to break Agatha out of Nosy Spell or kill her while she is under its influence? Because (and this is my assumption) 1-No one has Chaos Magic, 2-Nosy Spell might hide Agatha’s location as well. And from episode 9, we now know it’s Rio’s power that actually breaks Agatha out. So Agatha knows this kid has Chaos Magic, and she knows he was lying about wanting to get more power.

But with the Seven coming, she needs to put the “Teen” mystery on hold. The “Nope. Too risky. No time” is more for her than for “Teen”. Remember, the last time she tried to mess with a young Chaos Witch, it didn’t turn out well. But she kept him by her side for the future when she got her power back and killed the Seven.

2. She suspected “Teen” is Wanda’s son the moment she picks up her pendant.

While being emotional and looking at Nicky’s hair, Agatha snaps back at Teen, asking who he is. Because it suddenly clicks for her. 

Chaos Magic is not some random magic. Wanda, who has it and is still an inexperienced witch, is capable of extraordinary creation and has her own chapter in the Darkhold. And she knows Billy has Chaos Magic. So someone who has Chaos Magic suddenly spawn between her 3 years gap. The possibility that he's related to Wanda is there in Agatha’s mind.

So she kept him by her side, to deal with him later when she had her power back. That’s why the “protective” behavior: telling people he’s her pet, familiar, etc. So what’s about the black heart thing? She knows “Teen” has a sigil on him, so the black heart should be him (can’t be Rio because Death can’t take a side), and she hides it not because she wants to protect him, but because she can’t have him down there with her and the coven when they sing the Ballad, aka when she tries to provoke witches and steal their power. She failed to absorb Chaos Magic once, god knows how this could turn out.

3. Gathering her coven quick and effectively.

Agatha needs Lilia’s power, that’s why she comes to her first. Divination witch is gifted talent, so she goes to the best near her. That’s why Agatha actually tries to convince Lilia to join/to help her with her coven list, by answering her questions.

With Jen, clearly Agatha doesn’t like her, so maybe she also doesn’t like the idea of absorbing Jen’s power, but the list said she needs Jen. So Agatha half-asses “convince” Jen. Noticing with Jen, all Agatha did was provoke and humiliate Jen to get her to join, and when that didn’t work, she quickly gives up because she doesn’t have time to work on Jen. It was Billy who got Jen to join but this belongs to a different post.

Lilia and Jen know Agatha’s reputation, that’s why with them, Agatha can’t use her manipulative tactics. But she can be with Alice, who is a young witch (probably around 20s-30s), so she did by using her “familiar”, Toto (lol). When Alice protests the idea, Agatha thought over and decided that she doesn’t need Alice that much, because a young witch doesn’t have much power for her to drain anyway.

She did make a mistake by telling Lilia how her power works tho.

4. The door to the Road appears, confirming “Teen” identity to Agatha.

(Now we know the Ballad to the Witches Road is a con Agatha run to take the power from other witches. That’s a crazy and success con I must say)

Agatha knows there’s no Witches Road, as she continues telling “Teen”: “The Witches’s Road doesn’t exist” - She told him at the start of the episode. So when the door appears, she knows it was created from thin air, a spontaneous creation, by Chaos Magic.

And she knows everyone there, all definitely don’t have this kind of power. So it leaves “Teen”, as he running into the scene.

Given her unique power, Agatha lives and survives by talk her way out or in of stuffs, so naturally she gets more information out of single conversation, and thinks of any posibilities there'll be for her to use. Billy's Teen persona is not even a match for her.