I'm quite sure she would beat her given she is at 100%. But I can only see positive things this week, she fought so well in all her matches and played great against Cirstea. It is a much better start than last season anyway
It is a difficult decision, but maybe it would be a good idea to skip doubles at the slams. It certainly helped Azarenka. A comeback of Vika and her would be great, but I don't know if Vika wants it and sadly I can't really see her winning a slam together with Petrova.