I think I have personally decided to go for Dream no more being canon for silksong, which does raise the obvious question of "wait so where's Hollow's shade then", and my personal headcanon is that Hollow is actually reshelled at this point and uh, 60% through destroying the city of steel.
Why? Well, okay, so for my personal timeline because I find it funny, Silksong takes place like maybe a week or two after dream no more. The void siblings needed time to recover, and are all kinda huddled below the void together. Hornet, as a result, thinks they're dead and does Poorly on her self-care. Between that and massive void exposure recently, she's in a pretty bad state already and this helps with her getting caught by the Choir.
Maybe a week or so later, the siblings are doing better, Hollow and Ghost are like "hey, we should go check on our sister and let her know we're alright!", they can reshell themselves, it just takes a lot of energy to do so. They agree Hollow should go first, and Hollow does!
Only to find out their sister got kidnapped during their 3 week nap. Because of course.
Both of them panic just a little before devising a plan, Hollow will stay shelled and go search the surface, Ghost will stay in the void to keep their siblings safe and search through various abysses to see if they can get any hints that way.
Now, Hollow having been raised during Hallownest's prime, knows of the city of steel. They know it's a place of many secrets and that they tend to have seers out in a lot of places, so who better to know where their sister is?
That's the thought anyways, but they get there, and the city of steel folks decide to imply they know where Hornet is but just won't tell, plus Hollow overhearing something about a weaver having being bound in service there, and they get convinced the city of steel has stolen Hornet and just start tearing the place down.
Anyways Hollow gets like 60% through that before Ghost actually finds Hornet and comes to let them know "hey no it's cool we found her actually" and so Hollow's just like "...ah, whoops, anyways bye I guess" and. leaves. Both of them decide to Maybe Not Mention this to Hornet when she gets back.
