I worry about your situation as it sounds like mine. Her mother needs to be parenting her more, if the father is tied up providing financially.
If her mother relinquished more of her role, supported you and backed you up, this might work. But she won’t. She is probably undermining you.
I think this is like mine, a ‘dreamworld’ setup. Where the father is somehow magically 50/50 or full time parent, but actually is still the main provider and out at work.
Dad is happy with this arrangement. He can feel mor fatherly. Feel like a good Dad. But doesn’t have to parent more / cut down work.
Mum is happy with this arrangement, as she gets maintenance, provision, but doesn’t have to parent more, and can easily undermine the SM as she knows her child’s loyalties are with her.
There is nothing in this arrangement that will make the parents want to change.
The child is losing out. She cannot be feeling okay as she is probably in a loyalty bind with her mother. Her father will side with her against you as SM. So she is indulged, but not parented.
You as SM lose out massively. You have a child who doesn’t want your parenting. A husband who takes you for granted. And a child who doesn’t care for you, and her mother who will always be number one above you.
I did this. Bought up step daughters for years who caused me problems with my own kids, and now totally ignore me as young adults. What was the point in that?!
Don’t do that!