Actually Flipkens is the toughest opponent in her quarter, both Dulgheru and Hercog are very poor hard court players. Kerber is probably more dangerous than these two. But Jelena has to win against Flipkens first
At least she will be better prepared this time and will know what to expect from Flipkens. The key to match is how Jelena starts the match if starts badly spraying errors left right and centre the head and shoulders will go down and it will expose her lack of confidence. Flipkens is a fit player who moves well and she will make at lot of balls and that will expose Jelena's lack of consistency.
I think it will be that Flipkens will be too solid and as a result Jelena's errors and her focus and concentration lapses will cost her the match.