TLDR: not very good.
Liv Warfield was a very good singer, but was a surprising choice for a protégé. I suspect that there are scores of women who could sing similarly, and perhaps the catch to opening for Prince is to _not_ outperform him.
The sound at the Fox was horrible. Far too loud, and a muddy and unlistenable mix. Too loud to forego earplugs, which is unnecessary and means you can't really appreciate musicianship. (I once saw Genesis and you could pick out the sound through the mix of Phil Collins picking up his tambourine.) A couple stood next to us during the encores: "We paid $500 for seats in the mezzanine and we can't hear a thing there!"
And Prince, bless his heart, was simply going through the motions most of the time. He spent an extended part of the first set simply triggering different samples on his keyboard and singing a few bars. Then he'd change samples and sing a few more. No rhythm; no segue; no real plan. …