Michelle's singing was mediocre
I honestly felt her singing was flat and too breathy. Though she is a helluva actor, but the singing was just fair.
shareOP -
With respect, you ever tried to hold an audience?
She didn't need to (a) have a great voice (technique & all that jazz) but she did need to know(b) how to interpret a song and(c) look conventionally attractive.
As a lounge singer, you can get away without (a) as long as you have (b) & (c).
For Rogers & Hammerstein and Sondheim, you need the great voice.
You're at the mercy of the director/MD for interpretation.
Appearance is less important as long as the audience buy you as the character.
If MP had a great voice, her character would've lost credibility.