You are completely off base. What you have been told is not only wrong, but likely, if followed, to undermine the case of the accused (your friend). Your friend needs to hire a lawyer immediately and the lawyer's investigator needs to interview the witnesses as soon as it can be arranged. There is no opportunity in the judicial process for a group of volunteer witnesses to offer their testimony before trial for the purpose of getting charges dropped. If something like that was attempted, you most likely would be politely told to go home, or, in the worst case, be directed to the District Attorney's Office where your attempts to help the accused would most likely be used by the DA as an opportunity to weaken your statements and otherwise fix the weak points in the DA's case to get your friend convicted.
A victim can talk to the District Attorney and express their wishes. However, the District Attorney can proceed with a prosecution if he has enough evidence to prove the case regardless of the victim's wishes. A criminal case is brought on behalf of the People of Colorado to enforce the laws. It is not brought on behalf of the victim and the victim does not have the power to drop the case.
You can reach Harkess & Salter LLC at (303) 531-5380 or info@Harkess-Salter.com. Stephen Harkess is an attorney licensed in the state and federal courts of Colorado. This answer is for general information only and does not create an attorney client relationship between Stephen Harkess or Harkess & Salter LLC and any person. You should schedule a consultation with an attorney to discuss the specifics of your legal issues.