I don't really think she would say "I am the girl that you lost to cocaine" if it really wasn't about losing a friend because of their cocaine habit. My guess is she was hoping this friend would hear this song and have no choice but to accept that she was talking about them. I say this because she states that she's tired of being their "crutch" and adapting to their behavior, and now she see's no other way to help them but to leave them so they might understand the severity of their situation. Furthermore, she says she's "a girl with a lot on her plate", meaning that she doesn't have time to deal with those with this problem, but she obviously cares about them since she's gone out of her way to help them up until now. At this point she's trying to use tough love to help them.
I agree with j-love's first interpretation.
I don't really think she would say "I am the girl that you lost to cocaine" if it really wasn't about losing a friend because of their cocaine habit. My guess is she was hoping this friend would hear this song and have no choice but to accept that she was talking about them. I say this because she states that she's tired of being their "crutch" and adapting to their behavior, and now she see's no other way to help them but to leave them so they might understand the severity of their situation. Furthermore, she says she's "a girl with a lot on her plate", meaning that she doesn't have time to deal with those with this problem, but she obviously cares about them since she's gone out of her way to help them up until now. At this point she's trying to use tough love to help them.