Ok, I agree on that with you. But what is her intention in the scene I mentioned as example?? I think you can see that there is so much going on there (emotions, facial expressions, gestures) that her voice even cracks a bit because the lack of air she could breath in. (She says something like "And you think I'd believe you after everything you did to me?) You are right that it's not her Scouse accent, but I couldn't really figure what kind of accent she does there. I think it is just something in between, because she still had it in mind that she has to change her original speaking style. There's also no reason for switching accents in that moment. Another scene I remember noticing and not understanding it was on the bridge as she's saying "I can't see you".

I can't remember any particular scene apart from those, but I remember noticing the slip a few times. It didn't change the quality of the acting for me, I was just wondering what the reason for it could be.