Step daughter problems

MRS.Powers408

My step daughter is the same age as my own daughter, 7. And I also have a 5yr old boy. My step daughter though usually lives out of state with her mom and is only with us a few times a year including the summer. Well this time she's here, I'm pregnant and hormonal and can't handle myself very well. ..she has always frustrated me but now I just feel so stressed with being 20wks along. She argues about every little thing and it annoys me. Also she bosses around the other kids and just has this sense of entitlement even though she's not any older than the others. My daughter is quiet and passive so she doesn't really stick up for herself and just does whatever the step daughter wants to do. My son and step daughter bicker about every little stupid thing. It just gets old. I keep them busy with as many activities as possible so that there isn't time for the fighting but...it's summer and there's also a lot of down time where they're just playing together at home. My husband and I have talked about it and we have open communication about it and have formed a united front to keep them all from fighting or talking back but... it's still his daughter that always wants to argue with me. (I only say "his" daughter here to explain the story, I don't think of her as just his not mine too).

Any advice? The stress is overwhelming. My strategy is to not argue back with her and just tell her how it is going to be when she argues but it's never ending and exhausting to have to deal with over and over again every day. Plus I don't want to come off as the mean step mother, I want to have fun with her too and not be strict all the time but she takes advantage in every way she can. She has her daddy wrapped around his little finger so it doesn't help that when he gets home at 330 she turns all whiney bc she knows he will not be as strict as me and will give in to whatever she is wanting (which is getting better bc we've been talking about things but still)

Ugh.