it was not the drug taking that was making her children unhappy, it was her lack of care and time for them.
They probably aren't entirely happy now she is bored and resentful (which she wasn't before, when she was happily doing as she pleased) but they are a hell of a lot happier. They no longer turn up at my house at 2 in the afternoon begging for breakfast. They are no longer inappropriately dressed.
So an action that has directly led to the mother's dissatisfaction (SS insisting she takes a child centred approach, rather than a her cenred approach) has directly led to an increase in the child's happiness.
And you could say this about many things.
When I was 13, my mother had an evening job. It made her happy. It did NOT make ME happy. She was out of the house until 7pm leaving me to look after my siblings, which in itself wasn't a problem but meant I had no social life. I was not happy at her happiness, I wanted her to come home and look after my brother and sister so I could go out, and I did not care how unhappy this made her.
My friend was raised by a childminder. She was there 5 days a week until 7 pm. The childminder used to put her in her pyjamas and she was put straight to bed when she got home. This continued until she was 11, when she was expected to go home, have some oven food, and sit on her own until a parent got back. Her parents did NOT financially need to live this life. They were really very very rich - they had ponies and a swimming pool - and could have dropped some hours and lost some money quite comfortably. They chose not to, and my friend resents being emotionally neglected by her parents.
A friend of my sister's is the oldest of 11. She came round sobbing when she was about 15 that her mother was pregnant again, and couldn't she see that there already wasn't enough to go around? I happen to know the mother socially - her mother loves having a big family, but at least one of those children has been made very unhappy by her decision.
All of these are normal family situations without a hint of a drug or abuse. In all of them, the "Mummy" was happy, so why weren't the children?
Children are not happy because mummy is happy, they are happy when their needs are appropriately met. If they get that with a happy mother, I'm sure they'd be pleased - otherwise I think most children will choose for their needs to be met regardless of how their mother feels about doing so.