So this wasn't in any way a thriller.
This was a campaign dressed up as drama saying that more care needs to be given to people put on medication, ie not just pills but support and so on. (Cant rmember the name of the actress who played the Doctor but the implication was she would be investigated.)
It was about 2 parrallel stories showing how close we all are (or women with multiple demands on their life are) to going over the edge. ie Abigail being killed was because of a mother worn out by lack of sleep etc.. Conne, not remembering what had happened, just challenged EW character as she just thought you are no better than me, and by projecting her problems onto EW in fact hit a nerve.
So the bit in the tree and other implausibilities were to show they were two sides of the same coin.
Not sure what Connie's sentence actually was, but would seem the explanation of total withdrawal from all drugs was the problem - and all the people who should have cared for didn't recognise the impact of her mother's death and her husband's affair. (Although by the end I wasn't sure if Nessa having an affair with Connie's husband actually happened or was part of the drug induced hallucinations.) And was not serving time in a prison but some sort of facility until she was deemed stable enough to be released.
But overall very depressing about women of a certain age losing any sense of themselves, unempathetic husbands, patchy NHS care, the worry of caring for children, and ... .
I definitely think it should have not been billed as a thriller and possibley come with a warning. Not so much the driving of the bridge as we see far worse in crime dramas, but whether some of it might have been quite triggering for some.