Your thread title and description of ‘stealing’ are very high octane. I opened the thread expecting to read about shoplifting or taking money.
“My kids have all been brought up knowing it's wrong to steal,
Repeatedly my husbands daughter thinks it's acceptable to go into the kitchen at night and steal food”
Are you suggesting she has not been brought up to regard stealing as wrong??
You say all the kids have multiple snacks during the day, do they have to ask? Is that the rule? If they can help themselves, all that is happening is that she is helping herself at night.
However, things are not right.
I am sure you are being a great step mum to her, and she is ‘fine’.
But the truth is however brilliant and fair you are you simply cannot fill the gap left by a mum who limits her contact with her kids by her choice.
That is such a huge void and abandonment in a child’s life.
I think You need to look more empathetically about where she is seeking to have small pieces of control or comfort in her life, and to gain a sense of those things for herself.
6 kids is a lot in a house. She may want something secret, just for her.
She won’t grow into a criminal, and your other kids won‘t start a biscuit frenzy just because she is doing this.
Relax, watch and remain sensitive to her.