Hyo has a notable reaction to the mention of the Cleaners in this panel, so the natural assumption is that she's thinking of Zanka/knows that that's where he went after leaving the Hell Guard academy
BUT there's also the possibility that she knows someone else in the Cleaners - thinking specifically of the theory that she has some connection to Tamsy.
I wanna bring up this artwork of Hyo before she joined the Hell Guard academy and how there's a figure in the background who looks like it could be Tamsy:
It's no secret that they share some visual similarities (very light hair, prominent eye lashes, similar eye color), so I wouldn't be surprised if the theories of them being related were true. (I'm particularly fond of the theory that they're both from the Sileia tribe that Noerde and Mildretta also descend from.)
Meaning that there's a very real possibility that Hyo actually has no idea that Zanka is a part of the Cleaners, which would make sense if Zanka didn't tell any of his classmates where he was going (he didn't seem to have any friends) and if the Nijiku's kept his whereabouts under wraps to save face - those are of course speculations on my part, but they seem reasonable enough given the context of the Nijiku family dynamic.
If all of that is true, and if Hyo ends up taking August's offer, their next meeting could be a big surprise for them both lol
Okay, so circling back to this post, I think the first panel suggests that Hyo wasn't expecting to see Zanka. This doesn't inherently mean that she didn't know he joined the Cleaners - it could easily mean that she simply wasn't expecting to see him at the Doll Fest/right then and there - but I think this lends to the theory that she might know someone else in the Cleaners and that's why she reacted the way that she did.
I have theorized in the past that Hyo might be the second angel. She's around the right height, she shares visual similarities with Tamsy, she is known to not have a stable job (so no one would miss her if she went missing for a few days), and, if she is related to Tamsy and there's some bloodline factor that allows him to travel to and from the Sphere, then she would be able to cross the boarder as well.
When Tamsy went to the Sphere to kill Regto, he notably didn't have a Watchman series item on him. He could have taken Amo's boots, but he didn't. Zodyl had his coat, Gountess had his necklace, Enjin had the watch, and Rudo's gloves and Regto's notebook are accounted for on the Sphere. Unless Tamsy managed to take one of those items without their owners noticing, there has to be an alternate way to get past the Watchman.
A popular theory is bloodline access, which is the only one that seems plausible at this point in the story, though Kei Urana could easily make up anything lol.
If it is bloodline, though, then Tamsy wouldn't need a Watchman series item to cross the boarder. And if Hyo is related to him, which seems likely based on how similar they look, then neither would she. It might also explain why she has the eyes of a giver despite not having a jinki.
(This is assuming she's not actually a giver - there are theories that she is and either lost her jinki or can't use it for combat, and I do think it's possible, but I'm choosing to believe that she's not until we're told otherwise since an established part of her character is about being a "genius"/a strong non-giver who outclasses givers.)
Having a bloodline connection to the original four apostles gives people a proximity to anima and vital instruments that could cause their eyes to appear like that of givers - this would also explain Kyouka and Goka, and might also suggest something deeper going on with Zanka since he did have light in his eyes before bonding with Lovely Assistaff.













