@Wolfgirrl 1800 votes on AIBU on a forum (with a large majority of members) that is well known for being completely unsupportive towards step parents and the complex dynamics means absolutely nothing to those of us who have insight into these dynamics.
If this post was on a forum where step parents were supportive, nearly all posters would empathise with the Op and understand why she felt the way she did. There would also be balance however and a complete acknowledgement that her saying an absolute no to this set up wouldn’t be the best solution. And advice would be given on how to navigate this.
I’m not entirely sure what happened to you, but I’d ask that you stop projecting your issues onto step parenting threads please. Posters like you are the reason I withdrew from the step parenting section. What happened to you is no ones fault, you’re not over it? Get counselling. Rubbish stuff happens to a lot of people growing up. The smart ones don’t go into Internet forums and project their issues onto other people.
Your insight as a stepchild could be used really usefully. To help give advice from the other side and help people arrive at compromises. You could also use these threads to actually seek to understand what can happen when you are the step parent in these situations. As that may also help you to arrive at some adult level perspective and not stay stuck in this angry child state that you appear to be stuck in.
The whole route for this problem is the Dh and the complete lack of dialogue/ convo with the OP. It’s disrespectful and entitled. Entitlement around NR children is a dynamic a lot of NRP’s have and it causes huge issues like this in many blended families.
There are many divorce statistics around second families where both partners bring children from other relationships to the marriage. They are sky high and the people who make it are the ones who operate as a team. First and foremost. That requires communication, compromise, active listening and a lot of hard work.
People can come on these forums and judge and be vile. Blended families will become more common and quite frankly as a society we need to become more equipped (as a whole) to understand how complex the dynamics and challenges are.
That includes not piling into someone from a deeply judgemental place. I can only conclude that a lot of posters on mnet are deeply unhappy. Less judgement people.