How to deal with a competitive female?

My sister (non-bio) loves to appose me. If I like something she likes something else or it's weird or ugly (what I like). then a week or two sometimes couple months later she will do or get the EXACT same thing or style etc. It annoys me so much! She bites off of my individuality things that I ACTUALLY like and I've had the same tastes for over the past 10 years...she has been doing this for the past 5 years. It's getting worse started with home decor, then to clothes, now makeup, hair and food! I have cousins who are a lot like me and a friend and I that share new likes etc. The issue is she is so cynical when it comes to almost everything I do or like or how I am in general. Then she goes and copies me. My dad said it's because she is a h** and she she's I'm a lady and wants to be seen and treated the way people see and treat me. So I'm HOPING to get some good answers from people who understand human psychology well or very well. SHE is VERY competitive with me and sometimes other females but mainly me she actually acts on it with me and with them it is mainly talk. She was alarmed when strangers copied her outfit and hair at a place she frequents but will copy me and very OFTEN tries to out do me. How do I know? because of her words and facial expressions. Yes she actually days her blank is better or she's going to get blank that's better etc. I am honestly looking for GOOD answers.