Taylor Swift used to crushing it in packed stadiums ... but, it was Travis Kelce's Chiefs which did the crushing Sunday -- dismantling the Raiders while she watched.

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The singer-songwriter -- who's kept a low-profile at her future husband's games this season -- was spotted sitting in her private box at the stadium.

It appears she's sitting with her dad, Scott Swift, too ... and, they watched a flaying by the Chiefs -- with one memorable NSFW moment from Patrick Mahomes in the 31-0 victory.

As you know ... Taylor has attended several games for Travis this season -- including one where she snuck in behind a protective screen -- though she didn't make an official debut until last week when she was finally spotted.

While it seems Taylor stuck mostly to the box, at least one of her soon-to-be relatives decided to walk among the people ... handing out friendship bracelets around Arrowhead Stadium.

One Chiefs fan posted a pic of their bracelet online ... with "Taylor" and "Travis" written on dice and the letter "E" at the bottom -- not totally clear what that means.

Taylor wrote "The Fate of Ophelia" for her man ... and, after this win, his team's fate could be to win another Super Bowl -- stay tuned.