Well, not officially. The U.S. Open will be her last junior Grand Slam.
True, this is her transitional year so I guess we can say she is still not a total pro. But in a few months...
Actually, she has turned pro officially IIRC. You can be a Pro and play Juniors (Taylor Townsend for example, Anett included) and being Pro simply means you get to keep your prize money instead of the tournament spending your money on amenities for you
In that sense, I am quite sure she is officially professional