It's not a laugh out loud comedy it's just got a humorous tone.
Rhiannon's character changes very suddenly to become suave and collected with the occasional random anxious moment weirdly quickly.
SPOILERS FOR EVERYTHING NOW!!!!
It also seems very contrived how Julia survives long enough for Rhiannon to start to like her.
I think the programme wants us to get caught up in Rhiannon's delusion that her murder is moral and that Julia will be happy to be her friend in the end. And in that sense it's quite good as with the story telling you that everything's great you almost forget the horrible hypocritical murders. I think I would've preferred more of a dive into her actions at the end; whether we get to see the killings again in a new night or maybe more time is spent on her realising that she is a monster.
And it's also strange when Rhiannon realises that Julia is also a victim but never realises maybe other people are bad because they're also victims.
I don't know.
I'd just have liked the programme to go a bit more indepth with her morals because it is already there, just not taken far enough.