Quick — look at TVTropes! Just read the definition! — then come back.
The trick is to make the world want to treat you well. You don’t have to be ojou-sama per se; you don’t need money or status. You just have to behave as if you possess these things. “[T]he key point is that other people treat her like royalty, whether or not she actually is.”
You need not play the ice queen in order to achieve this. In fact, it is counterproductive in my experience. Ice is for those who have offended you in some great way. Ice is for freezing others out. You want them to come in, for a certain value of “in”. Your charm had better be genuine, even if it’s an example of silk hiding steel, which is another post altogether. And you don’t want to be rude or vulgar around anyone you don’t trust, in a setting where that’s just not done. Time and place, my dears! Time and place!
Sweetness is perfectly permissible. I get away with calling a lot more people “darlings” than most. I mean it, too. It’s one thing to hold back pieces of the inner self, that vulnerable creature, but to create a mask — a lie? Lies are hideous. Lies make their tellers ugly on every level. Unless you’re dealing with state secrets, for goodness’ sake don’t lie. Be real to the people around you. Don’t give out compliments you don’t mean. Don’t exaggerate your history; don’t inflate your importance. A little humility goes a long way.
Some of us, you see, are unsuited to brute force. Some of us prefer the subtle approach. An ojou can hide what makes her flustered and uneasy in society; an ojou doesn’t have to turn into something she’s not in order to win over strangers. Goodness, even the wealthiest women in our society forget how to be ojou. Rise above. Remember that you are a person deserving, at the very least, of respect, and remember to give it as well.