in the second act, she gets up to sing in a club in the Village and announces she's going to play a song she just wrote-"It's Too Late". She cowrote it with Toni Stern, who's unmentioned. No reason to distort facts just to entertain.
If I remember correctly, her friend in the band asks her to come up and join them and in doing so, asks her to sing "her new song" (or something to that effect). I'm not sure making the distinction is completely necessary for the scene as it would require adding more backstory that really isn't that relevant. And in the scene, it's not really distorting facts. It sounds like something someone would say when addressing the composer regarding a song she composed, even when the lyricist isn't present, especially in such an atmosphere. Such editing is necessary when constructing any musical biography. There is not one musical based on true events that includes all the details. And for the purposes of Beautiful and its story, It's Too Late is a massive hit that should be in the show, but the mention of Toni Stern would either be a passive reference with no explanation or start a tangential backstory that would start to derail the plot. Did Toni Stern sue? Was there a previous lawsuit that prevented mentioning Stern in the show? How would mentioning Stern for that moment benefit the story?
At any rate, I don't think Beautiful's book is a solid piece of writing nor did I find the show remarkable outside the performance of the lead (I saw Abby Mueller on tour). But I could understand why it may have been nominated for the Tony over If/Then. Neither held a candle to Gentleman's Guide, anyway, so the point is moot.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian