Hi, I'm new to mumsnet but I feel my partner and I could really use some advice.
Firstly, he has 2 children with his ex, he has them for 6 days every fortnight, picks them up from school on Friday and drops them off at school the following Wednesday morning. Jack is 6 and Jess is 4. I love them both to the end of the earth. Jack is usually well behaved and causes no problems at all. Jess on the other hand, and I hate to say this, can be a complete nightmare 
She will defy us at every turn, even if it is just something small, and I refuse to pander to her. I don't want to teach her that she can always get what she wants. I sometimes feel so harsh but it escalates so quickly. One of us can ask her to pass her something and the next minute she's screaming blue murder and crying her eyes out.
Also, and this is the issue that is really getting to me, is the lying. Now, I know she is only very young, but both myself and my partner have spoke to her about lying and the consequences but she does it again a couple of hours later. She's lied to try and get Jack in trouble, she's lied about doing something I specifically asked her not to do and other numerous things. It's not as if it's a one off. Almost every question we ask her she's lying to us. And it absolutely riles me. I know how horrible that sounds but it really does make me so so angry. I can't remember how my mum and dad taught me and my brother not to lie but I know that it was something that we were taught from being very young. I don't want to be the evil step-mother but I feel this is something we really need to tackle. I just hate how it usually ends in shouting and crying
.
Any advice please? Thank you in advance.