She's not playing tennis with that thing. That's some tool for building up the arm muscles, and it is heavier than racquet. She used that tool during the 2008 preparations for 2009 when she practiced with the Southern American coach whose name I already forgot.
I also think that it is older picture, but I found it on the website that Mish posted the link to. Maybe other pics are also older. I couldn't believe my eyes that she's practicing with that shit again.