I think this is how toxic relationships with drug/alcohol abuse work. They fall out dramatically a few times, violence, public fights, getting everyone involved. Get back together, tell everyone to mind their business. Happens again, they loose friends because they won't stick around if the person won't listen to advice, don't want to see it, sick of getting dragged into it. Sometimes an incident happens that's unforgivable the person just won't go back. I thought Rosie's SH and SA would be that considering she blamed Louise. But when that doesn't happen they resort to cleaning their life's up, no drink, no drugs, nights in doing couplely things, days out, any distraction really that makes it seem like they are happy. If that doesn't work it's usually right well we will cut this out our lives, this person, we won't go here anymore, we'll never leave each other's side, change my number, private my social media, get help, go to therapy. There's always something that they will try to fix it. There comes a time when all those couplely things aren't fun, there's only so many Saturdays someone can spend watching romcoms and baking fairy cakes. I think it'll be Louise who wants a sesh before Rosie. It'll be awww babe I'll only have a couple I won't get smashed then boom a public outburst like last time. They've no friends to tell about it because nobody can be arsed. There's nothing left to change or fix. It usually ends up with someone being very hurt or traumatised before they walk away.
I'm speaking for experience and from watching a friend go through it. I'm still waiting on her to see the light and leave her partner and I'm telling you it's hard as the pal who always picks up the peaces.