I'm sorry your daughter is dealing with this. The situation you described, where a minor stole an unflattering picture of your minor daughter from your Facebook page, zoomed in on her face, and posted it in a private group chat to make fun of her, can raise several legal issues in Colorado.

Under C.R.S. 18-9-111, for example, harassing behaviors such as unwanted physical contact, obscene language/gestures, stalking, obscene electronic communications, repeated phone calls, and repeated insults are prohibited. It imposes penalties ranging from a petty offense to a class 1 misdemeanor depending on the type of harassment. Additionally, if the harassment is motivated by bias against the victim's race, color, religion, ancestry, national origin, disability, sexual orientation, transgender status, the penalties are enhanced.

Other actions you can take include sending a cease and desist letter, or seeking a protection order. Often, a cease and desist order will cause the offending minor to remove the content and stop the behavior.

You should document the incident thoroughly, including taking screenshots of the group chat where the image was shared. Reporting the incident to the platform used to distribute the image could lead to the removal of the content and potential suspension of the offending accounts. If the group chat is connected to a school, it may also be worth notifying school officials, as Colorado schools have policies against bullying that extend to online behavior.

Only a judge or jury can determine if the conduct is a breach of a particular law. I would suggest speaking to an attorney to discuss your best course of action and how to move forward.