ETA: Wow, L., I wrote my original response before your SWH. You are in an emotionally abusive marriage. You deserve better. You want ideas from us to help you get him to understand, but you can't make someone like this understand or change. You can't make someone be what they are not. And he does not seem to be a good man. Get yourself into counseling. Call the local women's shelter for referrals to a counselor. They can help you form an exit strategy and provide you with support as you untangle yourself from this mess. Good luck to you.
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L.,
There's a lot going on here besides messy bedrooms and kitchens. The first thing is between you and your husband. Seems that your communication with each other could use some work. You need to be on the same page with your parenting, your finances, and your respect for one another. These issues need to be addressed because, if not, they WILL affect your family--- even after your 18 y/o step-daughter moves out. All of the younger children are watching how you and your husband interact, and it will set the tone for what follows in your family for years to come.
Find a good family therapist (LMFT for Licensed Marriage and Family Therapist) or psychologist who does couples/family work and get working on this.
The other issues relate to blending of families, and therapy will help with this, too. I don't know how long you've been married and whether you had children you brought to this marriage or if you and your husband have children together. From your post, it sounds like you also had children before you and current husband married. Either way, you are a family now, and it takes a while for blended families to find a way to work together. There is no one specific time, but it is a process that develops over a period of years, and much depends on the people involved and how willing they are to make things work.
The thing is, you guys are already on a negative path in the way you relate to one another. From what I read here, it sounds like in your head you've set up a scenario where it's dad/daughter vs. you. You've got to get out of that way of thinking and realize you're all in this together now.
You can't demand people (especially adult people) into doing what you want them to do. If you want your SD to respect you, you also have to respect her and the fact that she and your husband have a special parent-child relationship that pre-dates you. This doesn't lessen his relationship with you. It's not an either/or proposition. It doesn't mean he loves you less, and blended/step-families need to get out of this way of thinking. BOTH of these relationships exist, and they are BOTH important and need to be respected.
This is all about compromising and finding a way to be together that is founded upon MUTUAL respect. You have to get to know your SD as a person, not just an annoyance. I get that you're frustrated with her behavior. But she is more than just a messy bedroom. Please try to get to know her as a person. If you love your husband, you should extend that love to her, and develop your relationship with her. She will always be part of your life. Don't fool yourself into thinking that once she leaves the house that all your problems will magically disappear.
That's not to say you don't have valid concerns. You do. Everyone (children included, within reason and respect to their ages) living in the household has to have some responsibility for maintaining the household. It is not unreasonable to ask that people clean up after themselves---especially in common areas like kitchens--- but after that, you may need to rethink your standards. If she wants to sleep in dirty sheets and jump over piles of clothes in her bedroom, why let that bother you? This is a pick your battles sort of thing. You're going to have to decide if you want peace in your home or you want everyone to do it your way 100% of the time. If you want peace, there will have to be some compromises. This is true in any relationship or family---blended or not.
If your husband had already committed to paying for college before you came into the picture, then you can't really change that. This is something you should have discussed with him BEFORE you married. However, you and your husband should be discussing finances going forward.
Please reflect on what I've said here. I'm a step-mom, too, so I'm not trying to bash you. Please get into therapy so you can all enjoy each other rather than living with stress and strife.
Wishing all of you the best
J. F.