Usue is a promising 14 year old who seems to have quite a lot of potential. She's born 28th October 1998 in Buenos Aires, Argentina.
From what I gather she grew up in Puerto Rico (she currently lives in San Juan) but is now representing USA. I assume she'll continue to play for USA when she begins her pro career.
She is coached by Frank Salazar at the Junior Tennis Champions Center in College Park, Maryland, a USTA Regional Training Center.
On the ITF Junior Circuit Usue's currently ranked #272 and is younger than everybody ranked above her. In 2012 she reached finals of two G4 events in Casablanca and Philadelphia.
Here's Usue's "Prince Who's Next Athlete" video from last year.