Well unfortunately Monaco doesn’t host or participate in state visits, because their diplomacy is handled by larger France. So that leaves them the occasional royal gathering, if the event is white tie/gala. Charlene either fails to attend, or attends bare-headed.
Monaco itself has modernized their gala events to be black tie in this day and age, unlike the days of Grace and Rainier where a small modest tiara could be worn for an event.
I still have hope that maybe one day we will see Charlene in either a family tiara or one that was gifted her, along with the riband of the Order of St Charles, and some gorgeous gown.