@Background Pony #83F6  
That’s not even mentioning the countless opportunities she must have had to strike down Spike or even the keys. I’m not trying to hate, Cinemasins has ruined me, and now I’m a jerkass critiquing plot points and stuff that are not as smart as they could be.  
But, you are right. She could have been replaced by a changeling or is one of Twilight’s spies. It could be hard to get into the group, but with access to some sort of secret spell, it shouldn’t be that hard. Age doesn’t mean wisdom or intelligence, but Spike is the grizzled veteran, he’s supposed to be smart.

@Background Pony #83F6  
No, I’m pointing out less than logical parts because lo and behold, next page night star just starts to transform (and they’re dumb for not saving striking it down with magic or claws while it does so or try to save gold lily, who is likely to become a victim on the next next page) has been with them from the very beginning, and there doesn’t seem to be magic for detecting this stuff after centuries, despite how smart Twilight Sparkle is with magic because they probably would have used it on all their members. And if there is some secret spell that prevents them from doing so, a detailed interrogation wouldn’t help Spike’s group if she had access to that kind of magic.

@Background Pony #C2C7  

Or maybe, you know, they have ways to perform a more specific, in-depth check/interrogation when they have reason to believe someone could be a spy? You know, one of the oldest tropes there are?
 
@Background Pony #C2C7  

You mean how Celestia and Discord always do stupid shit and are surprisingly ignorant about stuff that is often obvious to us despite also having lived that long in the show?
 
@Background Pony #C2C7  

How do you know its easy? Are you psychic? Because it could very well be that they actually have very effective ways of analyzing and hand-picking members, and inserting somenone in their group took Twilight/Changelings years of effort, planning and/or maybe some secret spell.
 
But no, lets just blindly assume it was all easy and they’re all stupid. Because hatin’s more fun, huh?
 
@Background Pony #C2C7  

Don’t quit your day job.

“The Pinkie sense is nothing to joke around with” Oh the irony.

@Background Pony #FF3A  
which would be immensely retarded cuase, well, fuckin dragon.

@Background Pony #C2C7  
dude same

dun, dun, duuuuuuun!

Make Night Star blow up in a shower of vanilla ice cream.
 
Why?!
 
For absolutely no reason.

Why do this in front of her? Now she doesn’t have to do anything and will look innocent. Also, you’d think Spike would be a little smarter after a thousand years. It’s a miracle his resistance group managed to survive this long if it’s this easy for one of Twilight’s soldiers or a changeling (or something else entirely) to insert themselves as double agents/assassins.  
Anyways, I predict Spike is going to die to show the seriousness of the situation.  
Looking forward to what happens next.