Stephan, if you want to sex your fish, please see the thread that I have posted to help you become your own expert on the subject. I have a link to it in my signature area called Sexing Livebearers.
The picture that you posted was not of a female close to a drop, it was a well fed female. It had a strong shape of a square in the front area of her abdomen with an unconvincing squaring off of the rear area of her abdomen. Please see the thread that we have here for judging your female. It can be reached by a link in my signature that will take you to a frequent picture of one of my mollies as she moves from one drop top the next. I tried hard in that thread to give hints each day along the way as one of my mollies moved from her first to her second drop called My Molly's Progress. In most of the pictures you can also see some of her fry from the first drop in the picture.