I think if they have a little Princess, she will definitely take the names of Henrietta and Margarethe. Possible other names could include Ingrid and Elizabeth
If Prince Frederick and Princess Mary have a little girl, one name that she could be given is Ingrid Elizabeth Margarethe Henrietta or another name which will incorporate Margarethe and Henrietta
I don't know if anyone has replied to you, but from looking at them they look like beautiful semi-precious stones, like citrines, peridots and tourmalines