ijustlovepuzzles -- a popular streamer best known for sharing her puzzlemaking exploits online -- will soon be able to flash her best smile when she finishes one ... because she made thousands at Kai Cenat's Streamer University, and she's going to get her teeth fixed.

We caught up with Gma -- that's all ijustlovepuzzles goes by, sorta like she's everyone's grandma -- about her good fortune ... and she explained she won the money because she helped a janitor clean up a cart of books he knocked over.

As with many things connected to Streamer U, not all was as it seemed ... and -- in a Hallmark-esque twist -- the person she helped turned out to be the influencer Zachery Dereniowski -- who goes by MD Motivator online. No one else helped the dude, so all the prize money went straight to her.

MD Motivator and Kai teamed up to give Gma $30K ... money -- along with an extra $18K she says she made from her new subscribers she got through Streamer U exposure -- which will go toward getting her teeth fixed and starting a puzzle company of her own.

ijustlovepuzzles wants to pay the good fortune forward, too ... imagining a company that prioritizes diversity -- and gives part of its earnings to people who really need the dough.

As for next immediate steps ... Gma says she's got some offers to collaborate -- but it's not all it's cracked up to be. Watch the clip all the way through to learn why.

Basically, just like one of Gma's puzzles, it sounds like everything's snapping perfectly into place for the streaming star!