9 Year Old Stepdaughter - Manipulating the System

Being a step mom is SO hard!
I had the most manipulative step son on this planet, believe me. He played everyone. Grandparents, his mom and dad, me, his teachers. You name it.
I couldn't even ask the kid to pick up his clothes off the bathroom floor after a shower without it starting a World War. His own clothes, 18 inches away from the hamper that was readily available. He would literally tattle on me then my husband would jump me because I was "picking on him".
OMG! Asking the kid to put his plate in the sink like everyone else did was considered corporal and inhumane punishment.
First of all, it wasn't a punishment. It's what the other kids did after finishing their meals. It wasn't a form of "discipline" either.
The main thing is for you and your husband to be on the same page.
My husband didn't back me up until the day he heard his own son telling me that he expected all his clothes to get washed, by me, by hand, in the bathtub.
From then on, my husband instituted the hamper and laundry rules and backed me up.
Little by little, it spilled over to other things as well. It took a while.
I actually really loved that kid and one day when it was just the two of us, I had a talk with him.
I told him that I wasn't his mother. I didn't want to BE his mother because he had a perfectly good one already, BUT....I did want to get along with him and when he was at our house all I asked was for him to do what everyone else did. No more. No less.
Telling him I had no intention of trying to be his mom turned everything around.
That and the fact that my husband was the one who explained the rules so it wasn't coming from me which only set me up for dealing with defiance.
I hate to say it, but sometimes, as a step mother, you see things happening and you just have to stand back and let them happen.
Like I said, my step son played everybody. It was obvious. I didn't need to nag or make a point of it. Certain people, my husband included, didn't want to believe that the kid would do some of the things he did. But, he did them and unless it related directly to me, I stayed out of it.
I backed off and my step son drew himself closer to me as a result.
He's also now an extremely successful adult who has worked very hard for everything he has. He turned out okay.
Don't give her a chance to tattle on you.
Go over the rules with your husband and agree on them so if she tries that he can say, "Honey...this is just how it's going to be. You don't have to like it, just do it".
That way, you're not the "bad guy".

The first couple of years is the hardest, in my opinion.
Hang in there.

I have always felt and read that the step-parent shouldnt be the one disciplining. My bf has 2 boys 12 & 8 so I hear ya! You have to have a discussion with your bf/husband about disciplining and that it should come from him. She probably has her own reserved feelings towards you stepping in, the last thing you need/want to add to that is resentment. I think you should support & enforce the rules, but not make or set them. Good luck and I hope you can grasp this situation soon.

If I misunderstood the statement and the mom grounded her then I apologize for getting it backwards.

First of all her activities with her mom is for her mom to decide. When she's with her mom you guys have no business telling them what they can and cannot do. That's interference with her parental rights. If it's something that's a danger to her then it's for the dad to decide to talk to the mom about it.

Second of all, you and the dad need to have a discussion about rules in the house and decide on a few basic rules and the consequences so that you don't have to make up rules as you go. After 15 months you guys should already have the idea of what you want to put in writing. You should not be put in the position of telling her rules all the time. Her dad needs to be the one doing that. It makes you the bad guy, it would be nice if you and she could be friends instead.

Put the rules up in a place that everyone can see. There can be 4-6 for her and 3-5 for the little guys. There can be a few general ones like everyone keep toys out of living room. And then some specific ones for her like doing chores on time.

Being a step parent has it's obstacles as you can see. I have a combined family as well. However my husbands kids are grown which brought it's own different type of issues but my daughter was 7 at the time we got together. I've learned from my situation and from others that the step parent can not be the disciplinarian of their step child especially if the child is older. You need to leave that up to your husband. Your job is to support your husband and help see that the child follows through but you can not instigate it. If you try to, you well be met with resentment from the child and the manipulation will take place. Now you may have a better chance of being more involved in the discipline with the twins since they are so young and you have them the majority of the time. Even though you are just trying to do what is best for the child, they don't see it that way, they see someone who is not their mom telling them what they can and can't do. So if you can have your husband set the discipline and you just help to see that it's followed through. Now this may change after some time when you and her relationship has matured some and she has learned to respect you. Not sure how long you and her have known each other so this could be all because she is new to all of this and she is testing her boundaries to see what she can get away with. Not sure I made any sense but hopefully I did.

I think you have to have a little sit-down with your husband and SD where you (you and your husband) clearly communicate that you two are on the same page and are basically acting as one unit. He knows everything that you know, and you know everything that he knows, and vice-versa. And then do it. Yes is may seem like over-reporting and over-communicating, but it's really about her relationship with both of you as one unit, not one relationship with you and another with dad. Let her know that dad will always get your side of the story, so if she wants to have the privileges that are earned with trustworthy behavior, she has to stick to the truth when she's talking to either one of you. You don't have to be harsh or go overboard, just a little bit of "head's up sweetie, we're onto this kind of thing and won't be gamed" (said with a smile). FWIW, this happens with bio kids too. We have a blended family of 4 kids ages 5-13 and DH and I are constantly in touch throughout the day over small details so that we stay one step ahead of the kids.

Regarding whether or not step-parents can discipline, as a practical matter a step-parent will sometimes or often be the one in charge. The parents have to establish house rules and communicate the rules and consequences to the children. Discipline when the step-parent is alone with the children should be handled as it would if a baby-sitter or other relative were in charge - handle anything immediate (time-outs for younger kids, sending and older child to his or her room to cool off, etc.) and then if there is a removal of privileges, that news should be delivered to the child from the bio parent when at all possible. That way the bp and sp have a chance to talk about the issue first and avoid having the bp override the sp and erode the united front.

Some books I would recommend are "When Two Become One Plus" by Sharon Anderson and anything from the positive discipline series. Start with the main PD book so that you and DH understand the approach fully and then you can move onto the ones for specific ages, the A-Z guide, etc. if you like the approach. It sounds like you've got a good thing going - keep up communication, keep your sense of humor and enjoy your family!