Disrespect in an 8 Year Old Girl

hello first I'm sorry denise decided to pass judgment without knowing you, we all have problems and that's why we are here. if I were you I would tell that 8 yr old, look! I know you already have amom, I by no means am trying to replace her, even though I am not your mom, I am an adult and you WILL respect me in my home. I would like a relationship with you but it's a two way street I need help. I would also have a serious talk with your signifigant other and tell himhis daughter is being disrespectful and if you want this to be our home and our life I need you to back me up. Tyry to find some sort of common ground witht his kid, and if all else fails you said ur on really good terms with her mother?? talk to her let her know you respect her and the only thing your trying to do is be her daughter's friend, you love or care deeply for your b/f and she is a part of him. she'll come around, good luck!

Give her relevant consequences and be consistent. Also give her lots of love and praise when she is being good.

How nice that you like her mom.

You are the outsider, you are taking over my lifeeeeeee! GO AWAY! YOU did this to our family!!!!! I want my mom and dad together, not you!

If she yelled that would that make her attitude make more sense? Unfortunately kids can't always vocalize what they are feeling and may not even realize that they are feeling that way. It isn't really about you, it is about them.
You don't say how long you have been with her father. If it hasn't been long then her reaction isn't surprising. And even if you have been with dad for a while, she is at an age when she will start bucking the rules.
I suggest that you take her out somewhere, just her. Sit and talk to her. Tell her that you understand that she must feel sad and angry about what happened to her parents. That it must be "weird" having you around. But that you want to try and make things easier for her. Tell her that you and dad are going to sit down and make out some house rules with consequences and rewards. Then you all are going to talk about it, make some changes (within reason) and post them. That way everyone knows what is supposed to happen. AND that you are going to do your best to spend a little extra time with her, getting to know her. This may mean 1/2 hour bedtime difference between her and her sibling, time spent playing a game with just her, or watching a 1/2 hour show, teaching her how to sew...something that is just for her. Take just her to the store.....you get the idea. =)
Kids get lost in divorce and new relationships. Encourage dad to spend some that that "just her" time with her too.
It's a fine balance between being a buddy and being a parent, even harder when you are a step. But in the long run it is well worth it for the child to give them balance.

We have a similar issue with my 12 year old daughter. My fiancee and his 11 year old daughter moved in this past summer. And my daughter was happy, mad, and scared all at the same time. I wish kids could just say "Hey I'm scared to get close to a new person because mom/dad and step-parent might split up too." or "I'm so mad because I feel like you're trying to take my Mom/Dad's place."
We do NOT allow rude behavior at all. She has consequences (usually loss of privileges) but I also sit down afterwards and talk to her about how she's feeling and what we can do to work on the rudeness that comes out.
My fiancee, makes sure to show her everyday that he's here for the long run and cares about her and her feelings.
Perhaps the two of you can spend some special time together. Have some fun and show her that you're there for her and are not taking her mom's place. Hope things work out for you guys.

8 year olds are like 2 yr old with faulty logic. They are testing the limits to see exactly where they are. They want control, but are afraid of it. They realize adults are not always correct. But they need love and guidance rather than punishment. I went through this with my son and it was tough. I told him i wasn't going to be talked to like that, I respected my self too much (rather than he can't talk to me like that - since he demonstrated he could). I would walk away and let him know he could try again when he was ready to be polite. Other times I offered condolence that he couldn't get what he wanted - it was sad and maybe next time he could try X Y or Z approach to make it work.

This takes time.Try to let her know you are not trying to take over her moms place. You are trying to be friends with the family. remember she will say stuff to hurt you because she is hurt inside. It is going to take time for her to gain her trust. Do not give up.

I think Samantha gave you really good advice.

The only other thing I'd add is to have a conversation with both her Mom and Dad to makes sure they agree with that approach and will be consistent in enforcing it with you.

I would lay out what is expected of her and what the consequences are if she deviates from it - and then be very consistent in the enforcement of those consequences.

Good luck.