Under appropriate circumstances, yes, police have the right to demand a private citizen go into their home. This happens all the time all across the U.S. In this case, had Ms. Good not argued with the officer, and had backed up upon his first comments to her, I believe this incident would not have escalated to her arrest. And, again, the video provides the evidence she was on the sidewalk, and within a too close proximity to the police action. Since you are using hypotheticals in asking how far is reasonable, I'll respond, hypothetically, that such a decision is appropriately relegated to the discretion of the on-scene officer of the police action, and depending upon the particular elements of the situation the officer faces.
What is “appropriate” concerning her property, her yard and her person? It isn’t like she was up in the cops face. When you are on your own property, and a cop tells you to back up, then can tell you to keep backing up until they force you into your own house, this making them the boss of the property, and thus limiting the ability to videotape and keep cops accountable (as they are human) which she has a right to do.
Whether or not she did or did oknot back up when commanded to by Robocop, he has no authority to force her into the house. He does not own her or her property - her yard.
Free speech rights and property rights trump cops. Cops serve the law and the people, not the other way around. Thus, the court sided with her, finding that she did no wrong.