Let me tell you about some reliable advice I received about the female mind about breakups, from a female friend of mine:
After a woman breaks up with a man and places him in the "FRIENDS" category, the man WILL NEVER LEAVE THAT CATEGORY.
If you want my own view man, here it is: She moved on. I'm sorry to tell you that, but she LEFT YOU. Even if you can't accept that, you must understand that she will NOT come back to you. Let me repeat that: she will NOT come back to you.
Take an honest look at how she has changed now though. Do you find a woman who is now into drugs and drinking carelessly with bunches of strange guys attractive? You have to also look at her signals she's sending you. She seems to be sending you NEGATIVE ones. Don't waste any more time thinking about her otherwise, you'll only put yourself through needless suffering.