Why is my old friend copying me? In photos and things like that and style..?

We were best friends for about 5/6 years. When we went to secondary school, people liked me. I was nice, cheerful friendly person. But my friend sort of kept me under her control. I wasn't really allowed to have friends because i was scared of being unfaithful to her. The girls liked me, but didn't like what i was changed into, because of my old friend. She was bossy. She has a bad home life and i think she sometimes wished she lived with us. When we were both 11 she tried to commit suicide, her family sadly fell apart after her grandad's death. I became concerned when she wouldn't answer my calls. I called her mom and she found her crying in her room trying to suffocate herself. She rethought and after came on holiday with us. She practically lived at our house. We laughed and shared some happy moments. Then everything kicked off. Everyone supposedly 'Bullied' her. I didn't see any of it going on. We told each other the closest secrets. Eventually i moved away. SHe started self harming and i didn't want to be around that. I got my own friends who originally liked me. They're my best friends now. She then stopped coming to school. She got another school after missing 5 months of education. Our school sorted it out. SHe got in the wrong crowd and we fell out again. In the holiday after i apologised saying we were good friends and i didn't want to part like that, so we were okay with one another. We haven't fell out since. After the last 3 years since, i've seen her twice. In the holidays were given. I spoke to her in last summer holiday, i told her about the boy who likes me (who she still likes but goes to our school) she said 'Jealous, your so lucky!' i said 'No not really, he hared me.. he's not nice' Im friends with him now, he still likes me, i like him. I sa her the other day then. I looked on her facebook pictures, their basically all the same as mine. Like one smiling with red lipstick on (like my idol, Marilyn) straight face with no expression and my eyes popping out because of mascara.. the same. She's also copying the way i dress too. My style. I like skinnies with a rock tee or most of the time i wear a short (cute, not slutty, i have this nice vintage 1940's look a like one which i team with a belt and cardigan) She's copied that aswell. I said 'Where did you get your dress from?' She said 'TK Maxx' i said 'Oh, well i got mine from there, the belt, shoes and the cardigan' She looked at me. She knows where i got them from because in one of my facebook pictures taken with my friends im the odd one out because im wearing a dress. My friend commented saying asking where i got my dress. She must of looked and went to the same shop. I got so angry. She also copies the way i look and she started to stalk the boy who likes me's facebook page. Why won't she stop? She's also adapted to my habit of talking D: