There is only one princess and that is Clarke Griffin. Maybe that is not your opinion, but it is a reoccurring thing that Clarke is called princess. She is called princess by Finn, Bellamy, Octavia, Raven, Jasper, Lexa, etc. It's a big thing.
Okay, now on to the actual tip.
DON'T USE THE NICKNAME PRINCESS FOR AN OC.
There are plenty of nicknames in the world, just don't use princess. That is clarke's nickname. besides, they called her princess because she was privileged, so if your character wasn't privileged then that should not be their nickname anyways.
I have used the nicknames doll, sweetheart, short stuff and babe. Other nicknames could be: sunshine, kitten, honey, shortcake, etc. You could also just shorten your OC's name (emma ; em, audrey ; auds, simon ; si, leon ; leo) or add a personal thing to it (emma ; emmakins).
I hope this helped!
