Its been a while but I watched this Japanese drama and I don't remember the name but the plot line goes like this:

The FL was a little tomboyish and used to always protect this cute classmate (girl) of hers who had a feelings for her. The cute girl not only had a crush on her but also was kind of manipulative and obsessed with the FL. She used to be absent from school for many days as she was a child actress. While all the boys crushed on the cute girl, many girls had a crush on FL instead of the boys. The ML had a crush on the cute girl too but as he talks to the FL, he falls for her instead. As he pursues the FL, the cute girl manipulates her to be with hers instead and hence the FL finally sees her obsession.

I don't remember clearly but I think the FL has was also given the nickname "prince". 

yes yes yes! this is it! Sixteen Syndrome. Thank you so much for replying.