A brilliant but destructive singer, struggling to get signed, must overcome her addictions before she destroys her band and her life.

Sounds like the sister could play a large part in the film so I'd include her here.
'A brilliant but destructive singer battles her demons, with help from her sister, in order to get clean and realise her dream.
You could even indicate what her sister is like, whether she is the complete opposite. May need to think about why she is a destructive personality, as this will be the ghost she needs to overcome.

Thanks, great advice.

"When a brilliant but destructive singer lets her addictions get in the way of her band being signed she must fight to get clean or lose her dream."

In the story, Her sister is the one fighting for her to get clean. (a bit of a battle of wills) She and her sister get in a huge argument. her sister get's in an accident and dies. It is the final straw that pushes her to get clean. Concentrating on two characters in the logline would probably make it too long.

The irony is there, as well as a good insight to the concept. The only things I would say is leave some room for the reader to be in suspense. Also reword it so that you can leave yourself some room to entice the reader.

A brilliant but destructive singer lets her addictions get in the way of her band getting signed, ______________.

Don't need "life" that's a given.

Room for info on another conflict or describe antaganist or etc. Less words more room for other stuff. Good Luck.