Has your partner been to treatment and also PHP and IOP? Then I recommend (Based on personal experience) sober Living for at least 6 months, it’s so easy to relapse after treatment if you go straight back to where you used, a friend sent me this when I was in PHP:
“don't know who needs to hear this, but if you're trying to stay clean and you keep going back and hanging out with old friends, it's probably not going to work. Old keys don't open new doors!” I know it will be difficult for both of you being apart but it’s better than the alternative, remember one day at a time!