Well no matter what you think, your Husband is the complete opposite and this is his, daughter.
So, well, there is a total contradiction or difference, in "how" you think your Step-Daughter should be and what she should be doing.
And he won't let you, have sleep rules or tablet rules, with his, daughter.
So that, is the problem. Too.
Per sleep-overs... kids do not sleep, when their friend or friends are there. YES, they are up at 2:00am. And think you don't know.
My daughter is 10 now, she has had friends over to sleep since she was 9 as well. And sure we have sleep times as a family. BUT, when she has friends over to sleep, I KNOW the girls will not sleep at their normal times. SO then, per my own daughter... I also KNOW that, it takes her about 1-2 days, just to catch up on her sleep and recover, from any sleep-over. AND a rule of ours is that, she cannot have anyone over, UNTIL she finishes all her homework, first, etc.
ALL the Moms, of my daughter's friends, KNOW that the girls will NOT BE sleeping at their usual times... when there is a sleep-over. And they are fine with it.
And the girls do often have their devices with them. ie: iTouch, tablets, etc. But mostly they are up all night, just chatting. MY own daughter knows... that she CANNOT go on the internet willy-nilly. Because, she listens, to our rules. And she is very good about rules. That we have for her.
But not all kids are. Then, when a kid is NOT good at adhering to their parent's rules... THEN that is where a problem will occur... with internet use and/or device use and what they do on it.
Some kids, can... self-regulate. Some cannot. It has nothing to do with trusting your child or not. It is about, a parent KNOWING their own child... and their child's own deductive and inductive ability to assess things. Or not. Because even if you 'trust' your child, it does NOT mean... that that child has fully developed ability to discern and track and control, their own behavior and judgment. The human brain is not even fully developed until 26 years old. And even some adults are just unable to make smart choices online.
So as a parent, you need to know that, about your own kid. What YOUR child's ability is... to carry out decision making and per their devices and use of it, etc.
And thus, handle the child accordingly....
And that also entails, consistently talking WITH your child, about their life/what they are doing/what their social life is etc., SO that, you as a parent with your child, have a good rapport and communication flow. And so that your child will not have to "hide" things from you. So, giving carte blanche trust to a child... is also a RESPONSIBILITY of the parent. To keep up with their child's activities. SO it is not blind, trust, nor unguided trust.
Because, trusting your child, does not mean just letting them do ANYTHING and doing it blind. And not knowing as a parent, what your child is doing.
Giving trust to a child, also means, being responsible, about it.
A parent still has the responsibility, to teach/guide/have rules with their child. Even if you trust them.