I hate a person but i have to put up with it?

I moved back to England( my home land) and ill have to Stay at my dad's house( im 15) or at least the nex mt 2/3 years but there is this girl here with who's i Had a thing and now she is acting all stupid like of he is better than me, worst part, if i say anything to anyone they will know we Had something, she isnt my niece but she is my step moms grandaughter, she is nothing to me blood wise and my step mom and my dad have only been toeher 6 years but ive known her for a month.

I ******* hate her, she is a ******* idiot plastic ***** who thinks she is better than everyone around her, what do i do? Stay here and try to go for my dream of being a film maker or do i return to Portugal? I think im in too deep to return now...