My thoughts are in blue, words to delete are in red, suggested rephrasing is in orange.

Eighteen-year-old Andie Shore is finally old enough to audition for the reality TV show I Can Dance!, which she’s dreamt of competing on since she was nine. I don't know if we need quite that much detail. The word "finally" above tells us she's been waiting a long time She convinces her older sister Piper to audition too, even though Piper gave up dance two years ago for college and her controlling boyfriend. Phrasing a little awkward here - she gave up dance for college, but did the boyfriend push her to give up dance? The way the two are paired here just comes off a little awkwardly Andie needs her sister because only Piper can help with her debilitating stage fright—the kind that makes Andie nauseous, breathless, and all around a total mess. Getting Piper away from her boyfriend for a few weeks is a bonus.

But while everything is easy for Piper, Even after being away from it for so long? who doesn’t even care about winning, Andie struggles from the moment the judges say, “cue music.” Failing her first audition, injuring a fellow contestant, and that annoying voice in her head saying she’s not good enough, are just a few things Andie never planned for. Worse is getting partnered with Tae Kim—the technically perfect ballet dancer she accidentally jabbed in the nose. Andie can’t stand Tae, and Tae can’t stand Andie. Unfortunately, all of Canada can tell. Unless they find their connection, there go the votes. So she failed an audition and is still in the show? This might need clarification

As the choreography each week gets tougher, the internet haters get meaner, and her hatred Echo here with "haters / hatred" for Tae turns to something else (something definitely not allowed on the show), I'd strike this simply b/c it doesn't make a ton of sense. Romance between contestants is always a plus for a reality show, and you don't have the space to explain why that's not the case for this show in the query Andie’s stage fright only gets worse, and not even Piper’s support Is Piper still in the running? can help anymore. She’s one switch-split away from cracking under the pressure. But if Andie doesn’t win I Can Dance!, she’ll lose her only opportunity for a professional dance career. Worse, she’ll never prove to Canada, to Piper, Does she have to prove it to Piper? Her sister seemed liked nothing other than supportive until this line and more importantly to herself that even with her issues, she’s good enough after all.

A lot going on here, and for the most part you balance it well. In the first para Piper's b/f comes up twice, then is lost completely. I'd argue for striking him from the query, if he doesn't play into the plot enough to appear again later. Piper's involvement in the show isn't mentioned past a certain point either, even though you infer that P is better than A to begin with, so is she still in the running? The romance is a little lost as well, since it doesn't seem to play into the plot much more than just as an awkward sidebar. If it's inimical to the ending and climax, get that in there. Some tweaks and clarifications, but overall you're looking pretty good!