This is a big mistake that many people make.  The case is the ‘commonwealth” or “state” and the alleged victim is simply a witness.  In general, the da’s office does not want to dismiss cases.  The prosecutor considers what the alleged victim wants but it is not what controls the case.  Many times, there are options if the alleged victim has a fifth amendment or marital priviledge.  Sometimes, having the alleged victim sign an accord and satisfaction may make getting the case dismissed easier.  In general, the less serious the allegations and the lack of a record may make getting the case dismissed easier.