Everything you've said is proof that she needs an intervention. A person is an adict when their drug(s) of choice interferes with their life.

Her mother isn't the one that is shoving pills and alcohol down her throat. She's doing it herself which means that she's not taking responsibility for her actions. The way she's taking anti-depressants is wrong if she is looking to stabilize her life. She's abusing those medications.

An intervention won't only put her in a hospital to clean out. She'll also have to have therapy where she'll be taught how to deal with her mother and all her other problems without abusing chemicals.