Her single greatest weakness is consistency. Her vocals are wildly inconsistent.
She can't sustain low or high notes, and outside of a limited range she never sounds too pleasant, but within that limited range her voice does take on magical qualities.
I feel like sometimes she over-sings and tires to belt out a note that would just sound better in her head voice, which is a gift directly from God, imo.
Another one of her big problems is she rarely sings on tune.
This isn't much of a problem for a rustic, stripped down acoustic performance, but it's important
for a rigidly produced pop-dance track. She doesn't support her notes with the pitch 100 percent so
it often sounds like she's wailing or out of breath.
Because of these things, her studio voice benefits dramatically from a light use of autotune,
which is used with prevalence on her records.
Being totally unbiased, 5/10.