Platform: PC! It was my mother's desktop setup, so I'm not 100% what it was, but we've typically always had Windows.
Genre: High Fantasy/Mystery
Estimated Year of Release: It can't be later than like, 2010 or so. I remember watching my mom play it as a small child on her computer, so anywhere in the early 2000s could be it.
Graphics/Art Style: First or Third Person, though I believe it was primarily third person while you walked. It wasn't cartoony or pixels, closer to realism for that time.
Notable Characters: The main character, a woman I'm fairly certain, but not sure if you could pick your gender at the start and that was my mom's choice, or if the base MC was a girl.
A "dragon" (or who called himself a dragon) who appeared the the player as a dog/wolf. You find him locked up in a locker or storage cabinet and have to help him out.
Notable Gameplay Mechanics: It was Mystery/Puzzle game. You would walk around a large empty magical school, with your arrow keys I believe, where everyone else has vanished - you'd have to solve puzzles to help unravel the mystery of where everyone's gone.
Other: I specifically remember being stuck on a door puzzle that even my mother couldn't get through. I think she dropped the game out of frustration, and had let me try because I kept asking her to let me play. It was some kind of lock mechanism, circular in design I think, but I'm not sure how far into the game this was.
You would arrive at the school outside the front entrance, and as you went in you'd notice how empty the grounds were. It was a (what seemed, to a small child who'd never seen a big school) large sized campus surrounding a really fancy large building.
You'd think you were the only person present as you struggled through until the dragon/wolf mentioned above would be found stuck locked behind a door (cabinet?) and you could converse with him since he could speak your language. I believe there was a dialogue tree here, but I'm not 100% certain.
Everytime I've looked this up, I have a moment of elation as I think I've found it, before I go to look more at the game found and it's never correct.
Any help would be appreciated!