I'm going to turn my back on my best friend
why do you want to turn your back on your best friend ?
because she's a total loser.
If you call her a loser, maybe she's not really your best friend. It's hurtful to do that to someone.
I don't really care what you think about it.
I think in the long run your friend will be better off if you avoid her. It's not nice, but you don't seem to treat her very well and you call her a loser. Just let her go to find better friends..