Twilight: “Blah, blah, blah…”
 
Celestia: “….. …Excuse me, but where is your new friend? She was supoused to meet us here a while ago.”
 
Twilight: “Oh! Don’t worry. I’ll go get her. You just stay here and um… Check the table and make sure I set everything up right…”
 
Celestia: “Okay…” Looks at the fork.
 
Twilight: (Shit, shit, shit, shit! I’m sooo dead! But Starlight’s gonna be dead first! How dare she stand me up!) Leaves the room.
 
Many, many hours later…
 
Celestia: “…..” (What the hell is taking Twilight so long?)
 
Celestia: “…..” Looks up at the clock. “…Almost midnight… Sigh! …I’m disappointed Sparkle… I expected better from you…”
 
Celestia: (Grades Twilight’s ‘Make a new friend’ report.) “…F minus.”
 
Elsewhere…
 
Twilight: Hears Celestia grade her report. “F minus… F minus… F minus…” Echo
 
Twilight: “NOOOOO!”

And here we can see why Starlight skipping this dinner without even telling Twilight beforehand was a total jerk thing to do. She had every right to be upset.

@Background Pony #5516  
she was so nervous they retracted into her body

Twilight’s wings are missing

@Jackarunda  
You don’t delay Princess Celly from cake.

Instead of lying, Twilight should totally have invited Celestia to the show. She could see for herself Starlight Glimmer’s new friend.
 
I half expected Celestia to finish up the episode with “choose your new friend over social climbing is totes cool, extra friendship point yay” too, but that might have been overly forced.

So, my long-time student and now fellow princess invites me to a special dinner so I can see how her new protege is getting along under her guidance. I get there, and not only is said protege nowhere to be seen, but my student is trying to fob me off with some bullshit stalling and excuses that I’d have thought she was above doing by this point? Yeah, I’d be pissed off, too. We all have our limits.

How uncharacteristically dickish of Celestia.

@RektPony  
Yeah, it was rude, but it does show how pissed Celestia was. She was really irked by this. But hey, sometimes people are just tipped off at things.

@RektPony  
Yeah, I mean, not that I didn’t like her expressions in this episode, because these are priceless, but…

Yeah Twilight you’re gonna die.

That’s a “So, you gonna fess up what’s gone wrong or are we gonna sit here inspecting cutlery?” face if I ever saw one.

Twilight was later found dead after being stabbed with a fork by an unknown assailant.

It was rude that she didn’t even replied to her. Seem like “original wriitng” for the cost of character assassination.

Celestia: “This sucks. There isn’t enough cake here. The other ponies didn’t even show up. My hooves hurt. I wish I was back at my princess castle.”

Celestia no longer give a shit about her after she became Princess and stopped sending her letters.

Celestia looks like she’s going to jab Twilight’s eye out with that thing.

The face of someone who makes time for you but was utterly disappointed with the affairs you brought.