That's the worst thing I have discovered on here, there's no fixed answer and it'll depend entirely on you two as people. My SO isn't in treatment right now and it is abysmal to the point where I am seriously contemplating what to do, because love no matter how deep on its own isn't the fairytale cure it's made out to be. I love my SO deeply, have for nearly a decade, but being shut out and pushed away and blamed for everything is testing what remaining patience I have left.
They may want to process this on their own and for some that will work, but if their lack of effective treatment causes relationship issues I'd be worried, like I am currently.