Amen, MAYA. This eight year old child has absolutely no control over her living situation; going between two households; two sets of 'rules'. I feel for ya, Liz. Being the step mom is not a cakewalk.
Ages 3,4,5 are some one of the worst ages for parents to split. But what is done is done and here you are....
Here's food for thought: Something I came across before..... It is sometimes the 'rebel' child of the family who cares the more. It's the one who speaks up; who protests. Now, I don't know if that's really true or not. But consider that a person who protests in however manner they protest is in a way taking the more difficult route....because in many cases it is simply much easier to "go along, get along". And while the 'go long-get along' method has it's place, it's not always the most functional.
The older girl may not be giving you much grief right now, but who knows what's brewing under the surface? I was that "go long/get along" child growing up....the "peacemaker"....the middle child; the one try and smooth things out. That's not always healthy either. And while my parents were not divorced and I wasn't going between two households or anything like that, there WAS dysfunction in the family. My next youngest sister was the rebel, the black sheep, the one who did not just fall in line like what was expected. She was my number one rival on one hand; but my best playmate on the other....We were close in age.
Looking back on all of that now, I see very clearly what some of the issues were and why she behaved the way she did....and she has had to work through the issues as an adult. She had very low self esteem as a child. She now works for a psychiatrist and whenever I need some good insight on a psyche issue I can usually get that from her.