Can Halle sing? If it's going to be a musical, she should be able to sing. She seems a little old for the part (Ariel was a teenager, I think.), but there have been many men who played characters who were younger.
And apparently she and her sister Chloe were discovered on YouTube when they were younger, and have since released R&B albums. I haven't heard their music yet.
I knew she looked familiar; she and her sister are on Grown-ish. I watched like the first three episodes before giving up on that show, haha.