I do not practice in CO, but I may offer some general advice. Generally, a court will not force a mother to change a child's last name. You could, however, petition a court to change the child's last name. You would likely have to convince a court the name change is in the child's best interest. Success seems unlikely based on your post.
Consult with a local, experienced family law attorney to confirm this advice.
A court generally will refrain from interjecting its own preferences into the last name of a child. Unless it is for the child's best interest, the court will never force a mother into a decision.
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