The thing they were trying to liken her "addiction" to was drugs. And I know you all know that. But when someone's on drugs, addicted, you can't trust anything they say. A friend I've had for 21 years and I just parted ways, so I know something about all this. He's a heroin addict. I can't stand by and watch this guy, who's basically a brother of mine, kill himself. I don't trust him. I won't lend him money, which makes him angry, and I won't enable him to use. I told him that it's obvious that his addiction means more to him than our friendship ever did. He'd promise he'd stay clean. And I so wanted to believe him... But I can't.
Tara was right for leaving. At some point, you have to stop taking the abuse they put you through. They're only doing it to give them an excuse to use again. I, for one, will not stand around and be that excuse. Willow straight up lied to Tara. She violated her trust multiple times. And then she used Tara as an excuse to go binge herself on magic.
I think Tara was absolutely right to leave. You can't help someone unless they want to help themselves. And look how Willow took Tara's leaving. She fell WAY off the wagon, but then she started to clean up her act. I wish my friend would do the same, but I don't think he will.