Long but PLEASE READ i need as many opinions about my friend?

so when i was 12 i met this girl who was a year older than me and we became the best of friends but she was very popular she told me and the very first thing she askled me was how far i went with a guy? no to be 13 and obsessed with hooking up? i was only 12 and not interested in that kind of stuff and so we hung out all the time she would tell me all her "sex stories" with multiple guys ..i just ignored it cause i really wanted to be her friend and be popular . she always would say mean stuff to me and treat me like dirt!..when she went to highschool i still had a year left in middleschool she basicly droped me for seniors at her school and we never spoke until now.. i am 21 and she is 22. she still cheats on guys and is on probation for OC use!! and all she has even worse moods like she always said mean things but its like she is 100% miserable she talks down about my relationship with my boyfriend and is very blunt about everything..how could somone become so messed up? she came from a great family and everything what is wrong with her ever since she was little she wanted to go wild , i thought it was a faze..maybe not?