Since she hasn't pulled out of Doha yet,it was probably that she didn't want to put the strain on the injury of playing fed-cup feb 9 and 10 and then starting Doha Feb 11. They really shouldn't have put the two a day apart.
Fan of Maria Sharapova, Serena Williams,and Novak Djokovic
I think honestly Sloane probably wanted some extra time off to practice and rest...especially after all of the matches she has played lately and her large amount of media commitments after the AO. I'm guessing she wanted to make sure not to have any further abdominal injuries and take it easy!