why does my boyfriends ex girlfriend act like this?

[Shannon]

i got back with my ex bf of 2 years after being split up for about 8 months. in that time he dated another girl for about 5 months. i've never liked her even before they dated & her dating him sure didn't help that. anyway, she is now dating his best friend (they're drifting bc of her) and she claims that she hates me yet i notice everything she does seems to be very similar to stuff i do. we don't follow each other on twitter but i know she sees what i post and vice versa. she copies the kinds of pictures i post, interests i have, the way i talk in my tweets, things i do on a daily basis, way i dress, the list goes on.i tweet about doing yoga, a few days later she all of a sudden took it up as a hobby. i got my nose pierced and then she talks about how she needs new piercings. likw WHY. i just don't understand why this is if she claims she hates me. other people notice it too and tell me so i know its not ONLY me thinking shes a psycho. i should also mention she hangs out with a few of his family members here and there and his close friends drifted from him and are closer with her. its like she doesn't go away.she says shes over it and doesn't love him or want him yet she wants to be friends with him and thinks its weird that i'm not comfortable with that. i've confronted her about the copying and everything and she stands by the fact she doesn't like me, doesn't copy, and doesn't want him. i'm not blind or stupid so i know what shes doing is definitely with me in the back of her mind.

can someone explain why she is acting this way if she claims all the stuff i said above? i've developed a terrible hatred towards her because of this and it's very exhausting to deal with.

[Ashlee]

jealousy.