Why was she like this?

I had this fake friend for about 6 years. she would do horrible stuff like get me to befriend her friends knowing they didn’t like me. and they would all (she would to) make fun of me in a group chat when i’d be with them. she’d share my secrets and more. i knew she was bad but i didn’t have any friends so i kept her around, which was my mistake. anyway, when i had a crush on the guy during freshman year, she was the main one who knew. but she tells me that she was talking to him romantically, which didn’t I really didn’t mind because how would she know that was him. Even though I’m pretty sure I showed her? But the way she would act when she found out it was him. For example, she’d call me specifically to rant about him in a good way. Which she would never do about anyone. Nor would she call me. Then if she texted me something about him and i didn’t answer, she’d say “oh (his name) said hi”. which would be false since you only say hi to people if that person was already talking/texting them. me and her weren’t so she was either lying or talking about me. I also noticed how she “dated” him for a week when normally she’d date someone for 2 days. But she ended up leaving him for his friend. Anyway, I stopped talking to her for a bit. And she tried to get me to tell her about my love life so she could get info. She stood at my table for 30 minutes even when i wasn’t talking, and mentioning people from years ago. I finally cut her completely out and she switched classes so she’s in my class now. She doesn’t talk to me but it’s strange.
Why was she like this?
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