Her character was written after the "vain villainess" stereotype, and accordingly, she often acts and speaks as if she were the most beautiful and intelligent character in the series. Of the trio, she is the most enthusiastic about capturing the "Dynamond", but ends up doing virtually nothing except bossing her two henchmen around.
Marjo appears to be very selfish and greedy as she always wants more and more diamonds and only for herself. She also has a very bossy attitude as she forces her henchmen to do all the dirty work while she lays back relaxed usually smoking her pipe. Marjo is a very arrogant villainess and thinks very highly of herself illustrated by the fact that she usually angrily interferes when her henchmen are failing only to end up causing her own humiliating defeat.