In 20 years, I've only worked with one person who filed a complaint and then withdrew it, and the prosecutor then decided to go ahead with the charges. In fact, that prosecutor succeeded in getting a guilty verdict. The case involved a young teenage girl who was assaulted by her father and decided to withdraw her complaint.
I'm a little ambivalent and divided on the issue. On the one hand, you have to respect the victims' pace, but on the other, when manipulation occurs, it's not easy.