It would be funny to have Sweetie to go just completely ballistic on her, berating her with accusations and hitting her legs all while Celestia is just
“It’s funny. You’re not even the cutest spy I’ve caught in this office, though you do come close. Remind me to tell you about the time I found Twilight in here.”
Celestia: Young Lady, You Parent will not happy to know this! and not forget Your big sister R.A.R.I.T.Y!
Sweetie belle: I am doom For sure! My parent will not happy but Rarity will in Rage! Yeah i am doom!
Celestia: i will tell them to go easy on you, cuz i teach you not snooping other pony shuff!
Luna: Your doom a been Double!(she be drug)
Celestia:………..
Sweetie belle: she drug?…..but she right!
Celestia: I will good my sister First….You help me and not punich you but i will still lecture you ok?
Sweetie belle: Ok but no tell to my sister and my parent!
Celestia: ….ok but next you Snooping in my stuff or other royal you will be double lectured and punich!
Sweetie belle: Diel!
With over 1100 years of experience, I doubt Celestia is going to throw out the baby with the bathwater. Sweetie done goofed, but I believe she’s about to learn a lot, rather than get chastised for it.