@soundtea  
You DO realize Chyrsalis acted off only for Twilight’s benefit/downfall right?
 
Once she realized she had someone joined to the hip with Cadence around, she knew she had to discredit them. She was careful to not act too rude around Applejack while she was looking, and she rightfully didn’t act rude at all around Rainbow Dash, who isn’t always humbled by royalty like the others, and has a good eye for bs. She did her research. Eventually Twilight drove her friends away because she lost control of her emotions, because Chrysalis controlled the situation and perspectives too well.
 
The one flaw in her plan is she didn’t drive Twilight insane enough to kill Cadence thinking it was Chrysalis. She was intentionally tormenting her to use killing force and snap. Had Shining done the vows, Chrysalis wouldn’t have nearly had an aneurysm beating Celestia.
 
Sending an unknown warning threat to Canterlot was an ingenious way to get the overly repentful Luna watching all night, and give Shining Armor an alibi for his headaches.

@platypusmac
 
The diagram of Celestia attacking Chrysalis shows the ground beneath them on fire.

@Corpse23  
…that’d be it: given that her attack poked holes in ALL the changelings, it must be some sort of shrapnel from hell - it would have ripped every single pony in the room to shreds, including Cadance, Shining Armor and the Mane Six.

@Masem
 
the comics sorta also explained that celestia was pulling her punches during the Wedding. considering if she alone blasted holes in chrysalis and her how many hundreds of changelings (assuming its one big AOE attack) and trapped them in an active volcano. then doing the same attack on her in the confines of the castle would have severely injured or kill hundreds of civilians including childrens attending the wedding.

@platypusmac  
An alternate idea is that perhaps she knew it was going to be changelings, and had Shining set up that shield as soon as she knew (which we know was at least specific to keeping changelings but not ponies or dragons and likely normal wildlife out); however, Chrysalis, alone, had already entered, maybe laying low for long enough after Shining started throwing up the shield to make Celestia believe there was no changeling threat.
 
There’s a lot of ways everything all still works, and in fact I think the Fiendship comic does a rather strong job of showing numerous possibilities of what Chrysalis was planning and why no one but Twilight recognized the difference at that point.

@Corpse23  
Maybe she knew that “someone” was going to attack… the Centaurs, for example (let’s be honest, what’s worse, the Changelings or an entire ARMY of Tireks?)… because she got an anonymous, yet reliable tip. From, who knows, a certain black bug-pone?  
That would have distracted her enough to not notice “Cadance”’s worst slip-ups…

Celestia probably knew the changelings were making a move hence Armor’s forcefield around canterlot. she might even knew that may have gotten in the city before the barrier was erected but did not know who they are posing as, me might not have taken in to account that the leader of the changelings herself has replaced the bride to be and was willing to be surrounded by the guards and the princess’ near all the time as the wedding day draws closer.

@soundtea
 
I still don’t see why being aware of Changelings existing (hundreds of years ago, never to be seen since) would make her magically immune to any and all deception. The only scene she shared with Cadenza was when she had fooled everyone with her wounded-gazelle gambit + Shining Armor’s explanations for her behavior. Even Twilight was convinced at that point.
 
Maybe if the comic had implied that Celestia knew of their recent activities in the present time I could see the problem. But it didn’t. Instead they lost track of what happened to the Changelings after the volcano escape, at least that’s how I interpreted the fact that they didn’t have info on how she escaped in their records.
 
@kleptomage  
Hey, maybe it’s the name of the volcano! Mount Volcano.

“inside of volcano”
 
Great proofreading.

@Masem  
Just saying. I could kinda buy her not seeing the posibility of a fake if she had never heard of changelings (which seemed to be the case for everyone). But given how wise she’s supposed to be and knowing of them attacking multiple times (and personally blasting them away once). You’d kinda think that if this comic was taken into account, she’d at least be a bit suspiscious. The previous open threat of invasion at the wedding just makes her ignorance of it worse.
 
At least there’s hopefully a good FF comic to look foward too.

@soundtea  
I would assume that the time Cele spent with Cadance was in her “teenage” years (based on the Twilight reader book, the Cadance/Shining comic arc, and other material) and once she was an adult (with a boyfriend), was less involved in her as her focus was now on raising Twilight to be her gifted student. So any change in behavior from teenage to adult years (that is, how adult Chryssy-as-Cadance compared to teenage Cadance) could easily be thought by anyone else as just growing up.
 
Keep in mind: SHINING should have a noticed a change since he knew her and was in much longer contact with her, but he didn’t - but that might be a combination of Chryssy’s skill at posing as her, and a bit of mind-control magic. Twilight as the only one to know the change is because she was distanced from Cadance for long enough to have a specific image of Cadance in mind and see the difference immediately.
 
And in terms of ACW: going off the discussion of what happened in Trot prior to the trojan horse, several prior attempts at a full invasion failed, likely due to that many being detected. But when she went in solo with the intent to weaken from behind the shield that would have worked save for Incitatus’ narcissism. So with the Canterlot ploy, her going in solo would have not set off any alarms to Celestia that Chryssy was involved - she knew there was a threat but had no idea what. Chyrssy played Celestia just as much as she played Twilight in the comic, which is what makes her a very dangerous villain.

@soundtea
 
Those are all valid points, but all those could be said about ACW even before this comic came out.
 
And you are forgetting that if they fled Equestria after Celestia dumped them into than volcano, then as far as she knew the Changeling threat was gone, so if you are so dead-set on taking the “comicverse” into account when analyzing ACW, you have to accept that she would not have suspected changelings because they were long gone by then.

@dynamicv  
The fact that Cadance was suddenly behaving wildly differently, the threat of attack, and Twilight saying that she’s acting really odd.
 
Celestia likely spent years with Cadance given that she’s her honary aunt. And she already knew changlings could shapeshift and decieve. She also should have at least known they bailed out of that volcano in the hundreds of year timespan if she bothered to check on it every so often.
 
If they were completely unknown to her, then ACW seems a mite believable, but according to comicverse, she already knew about them. It wouldnt be hard to assume she would at least give a scan of some sort given the distinct possibility of an inflitrator.

@soundtea  
No. How would simply knowing about the Changelings’ existence hundreds of years ago help prevent Canterlot from being invaded in the present? Celestia didn’t spend every waking moment watching them after she fought them and had probably not anything about the Changelings since she stuck them in that volcano and they escaped to beyond Equestria.

@soundtea  
Don’t know.
 
Maybe she’s hit a ceiling on that already.

Wait a second…
 
If Celestia already knew about them in comic verse, doesnt that make her even dumber in ACW?