A victim of a crime is technically a witness to a crime when it comes to the criminal justice system. The state/district attorney's office does not work for the victim, ie. The State of Florida vs John Smith, not Sally Jones vs. John Smith. They try to take the victims' desires into consideration, but bottomline it is their decision. That being said many states, like Florida, have pages and pages of victim rights, although not inforceable.
The victim is treated just as any other witness to the crime itself, granted one would hope (and assume) that all parties involved would be conscious of that victim's emotional state (especially in personal crimes) but it is not legally required. The victim can be subpeanaed to testify even if they do not want to or want to press charges. (Many common examples of this are in sex cases; either against a family member or an older boyfriend/girlfriend in a statatory case.)
If you need a different answer, could you be more specific?
thank you! this gives me more of an idea on what to write :)