Note that this list is not comprehensive. I picked out a few examples of each kind of error or problem I found. Of course, not everything is a black-and-white issue; this is not a list of things you have
to fix, but take each under advisement.
>having audience with her//
Usually, that's phrased as "an" audience.
Right away, a lot of your verb choices tend toward the stagnant. You have 8 "to be" verbs in just the first 5 paragraphs. You're killing the story's momentum before it even has any. Most times, it's not hard to rephrase a lot of these things with active verbs, in the narration at least. You get leeway for dialogue, since people don't take fancy routes around such verbs, and the dialogue does need to sound natural. But as for the narration, the more active you keep it, the more interesting it is.
The beginning is also very generalized. Someone waiting to speak to Celestia is common enough that it doesn't stand out. So what can you do to make it pop? Well, look at what comes next. The narrator says she hasn't been here in a long time, and she enjoys looking around, but the detail level is so vague. If you'd just returned to a place you knew very well after being away for ages, how would you react? You'd notice lots of little details. You just mention generic things like rugs and marble floors that are stock pieces for a castle, and we don't even get a description of what any of it looks like. Impress me with how grand it is. Tie it to her personal experience. She's going to look at things that mean something to her. She doesn't just see the rug. She sees it still has the curled-up edge she used to trip on when she was young. The clock on the wall that none of the staff could ever seem to keep properly wound. A vase she remembers is gone now. Did it get broken, or had Celestia only kept it there to humor her? This is the kind of thing I'm looking for. Make this a very personal experience for the narrator, not some routine errand, since you haven't described it as one. (Actually making a routine errand interesting is a whole other topic.)
>Still, the same rugs and tapestries adorned the halls. The marble floors and walls were still//
Watch repeating a word that close.
>the guards and servants that walked the halls//
When referring to sentient beings, it's customary to use "who" instead of "that."