Hi Nellie, hope you dont mind me butting in right now but have only just caught up with your thread. Best advice from a step mum of 7.5 years this time and 4 years with ex and his children is......
DONT COMPROMISE YOURSELF,,, from my experience if you do you will build resentment.
Never say a bad word about thier mum in their ear shot.
Give them love and support and BOUNDARIES!!!!
Do not allow them to abuse you, dont try and be their mum or friend try and be a great young Auntie type ie, role model/mentor, someone they can rely on.
Personally for me, i was not comfortable with the kids in bed with us and made it quite clear to my dp, strangely at the time i thought it was unnatural as they were 7 & 8 and not mine. And i still have to say that i felt it was unnatural however now dp and i have our own kids and our bed doesnt represent the same thing to me anymore
Being a step parent is really really difficult, there are times that i resent there impact on my life and my kids life, i dont resent them because they do bring enormous pleasure but it does add enormous issues etc that frankly are sometimes just too exhausting, but thankfully i do love them dearly, they love me too and they adore their half brothers. After 7.5 years relationships with their mum are almost amicable most of the time and i would actually rather have them full time or for longer stretches than the upheaval of weekends but then again he ho!!!
In so far as the sleeping arrangements are concerned could you suggest that she is reaching an age that a) perhaps it is inappropriate to sleep with dad b) she may well be subconciously dividing and ruling between you and her dad and that isnt very healthy.
I wonder if you could suggest that a friend comes to stay next time in her room with her for a sleep over, i wonder if it may help her feel less isolated in your home and help her feel like it is hers. Do you think she feels it is her home to ? You know it may also be that your dh needs to be close to her perhaps he could stay with her for a little while in her room until she falls asleep?
Hope some of this helps, and remember you are not alone, bad or mad!!!
The hardest thing i had to deal with was recognising that i had deluded myself into thinking that i would love my stepchildren just the same as i love my own. I still hate to admit it (and i wish i was angelic enough not to feel this way!) but i do love my own kids that bit deeper !!!!!
Is your sd coming this weekend?