Saw the new EqG short, Fluttershy musical...
She has shown she's quite capable of singing in front of a crowd. She just needs a villain to defeat, hah. And friendship magic helps, too, at least from my viewpoint, but yeah, some settings have enough of that certain magic, others maybe not. I can empathize with her great potential that only comes out when the stars are aligned, so to speak.
Soo, being a Pinkie brain, I would have told her that there's no reason to be afraid of singing in front of crowds, because the only difference between crowds and crows is an added d, so since she is neither afraid of birds nor of the letter d, all is fine.
Also, wait until she learns about the fourth wall.