celestia is know for forgiveness , guidance and knowledge! the forgiveness is what luna love form her! well is normal! celestia use to be the user of kindness, laught and magic of all element of harmony! but can be honesty , generosity and loyalty too! well luna learn all them too form her big sis! but is not easy for her! luna be in the shadow of her big sis for long time! her big sis good on everything! all thing luna try celestia do better! or worst luna mess up! by the time luna become better on what she not but she still a long way to gatch up celestia! but no mader she try she be in celestia shadow and pony only looking celestia! and one day the nightmare start and celestia learn in the hard way! is the reason force celestia change! is what celestia to teach a sunset but sunset dont learn it and fail and run away!  
celestia dont want the pony make the same mistake of her or luna to protect them! is reason equestria is lovely place the ruler learn for the mistake and become better for thos who live in equestria! not like ruler on own world who dont care of us! thos jeck care only money!

@Background Pony #9C4D  
Maybe she wasn’t 100% sure Sunset was trustworthy. She probably still remembers how Discord screwed her over and sided with Tirek.

@Background Pony #9C4D  
happened in ATLA too when zuko was asking iroh for forgiveness, she was probably thinking about what she was gonna say to her

@Background Pony #A3F1  
No kidding, considering that Celestia likely was more mad at herself, but in Sunset’s case, she just felt she HAD to try to prove herself as Princess Celestia’s top student, like how Twilight was early on when she was obsessed with her studies more than anything.

Celestia sure didn’t make it easy though. Standing there all wings out and stern gaze.

@lasty  
Good point!  
_{Well, I think it is, anyway. Headcanon accepted, if nothing else. :3}

Well, i guess everyone got what they wanted.

@Background Pony #9C4D  
Maybe she was waiting to see if Sunset would pull the old “Princess Celestia, I’m so sorry. …sorry you’re such a jerk! Ha ha, I’m the best” before embracing her. A princess can’t be seen falling for that gag, it’s just unseemly.

Was there any point to Celestia’s stern looks beyond making the scene needlessly dramatic? All things considered, I’d have been shocked if Celestia legitimately was still mad at her.