Thank you for your good question!
In life there are no recipes. Moral codes and scriptures; usually are good about giving “recipes.”
It depends on the circumstances and depends in what the role is calling in you at that point. That role will act according to your stage.
Whether we “try to help” or not is not the issue. To “try to help” is another way on displaying our hidden “ego.” We want to become “saviors.”
On the other hand, to mediate out of concern for the well being of those involved, is a different matter.
Righteousness is dictated by your inner feelings first. If they are right, then your mediation and behavior will be right as well. Otherwise, you will witness that your mediation will bring further conflict.
Likewise, if you decide “not to act.” It could be sheer indifference masked in the nice label of being a “detached observer” or sheer egotistical “I don’t want more karmic accounts” or it could be the way to bring a good resolution of the issue, when they work out by themselves without further intervention.
“Be” right and the doing will come accordingly. No recipes allowed.