I also think the 999 call will be the downfall - not just because of how calm she was, how she quite crossly told him to "turn over" which to me implied she could see blood but also that angry scream she did in the background - not a wail that was angst filled but very angry.
Don't get me wrong, he was abusive, arguably did far worse over a period of time to her and she likely snapped. However I don't believe she didn't see any blood and therefore knew he was in need of an ambulance and should have said there was blood to the caller.
The bit that I don't think we will ever know is if he was strangling her by the sink. My gut says yes. I think she might even have got a knife in the way she described by reaching back (I feel the cups not being moved isn't a sign it didn't happen there, it could have been half a meter to her right so not directly by the sink just on that side, for eg). My gut says she knew she had a knife and lashed out either while he was strangling her or just after. Then possibly felt relief, dissociated a bit, mentally justified it - she was obviously drunk which would have made it all less urgent with so many things going through her head to process. I am not sure whether this means that it was self defence or not, but I do think she knew she should have called the ambulance and he might have survived. That for me is the crux. In the last episode they proved the guy went out and came back with a weapon after strangling her, yet he got off with manslaughter. It feels fair for her to get off with manslaughter too if we are applying like for like (although I did think he had clearly premeditated a murder where it is not as clear here).
As for the women who are saying they had domestic abuse in the family and because they or their mum didn't kill their partner she must not be heard as a victim, it feels like survivors guilt. The guy shaking his head and commenting that it's all rubbish who hangs about with them has also not thought about what his mum went through, just that "well she didn't kill him so..." this simply can't be the mindset that people who survive abusive households tell, because they all think we wouldn't expect them to side against the abused and that therefore they are "thinking critically" when in reality it is the opposite and they are reacting to protect the abuser by not seeing it as bad as their own familial abuse. She had to be "punched in the face" goalposts, for eg. I didn't like also how she went on about how she admired the other mixed race woman as a sob story distraction from her own loud verbally obnoxious actions and what the guy was sharing beforehand. That woman simply can't listen and challenge her own pov - she shouts loudest and stops listening which is why they all get so frustrated with her. I hope her mum sits her down after this and talks to her properly about how she was abused and how she reacted, as it feels like she was protected from a lot of the realities to have such a naive view on what a domestic abuser looks like and how victims react.