One more thought!
Your daughter experienced an extremely abusive living situation for a year and a half. She may have thought it would never end and may not trust that you will be there for her always. From her perspective, you sent her away once and she is likely afraid that you will send her away again at any time. It is a common abandonment symptom to push loved ones away and misbehave because the process of re-attaching is too scary. (I can't relax because mom might leave me in a scary place again!
Age 8-9 is an age when children normally misbehave and push at parents more intensely than before. It is a time when they are becoming more self aware and aware of the world around them. Often there are more nightmares, daytime fears of being kidnapped, fears that parents will die and leave them all alone. This is a normal developmental stage. And your daughter was living in a nightmare as she entered this stage. She did not get daily reassurance that she was ok and that her parents would hold steady for her.
So, she could be pushing for that reassurance now. She needs you and your husband and mother in law to show her that you are rock solid. You love her. And that her behavior is not ok, but your love will never change, no matter how disrespectful she gets.
I assume she does worse than what you have described. Leaving Chapstick in pockets and not eating dinner and arguing back are mild for what she has gone through. (In my opinion)
This stage of development is a time when learning practical survival skills helps kids feel more secure. So learning how to make her favorite meal (and inviting her to cook that for the family if she wants to), learning how to run the washing machine and care for her clothes (removing chap stick too), learning to garden, vacuum, build a fort, use public transit, etc.
All these help this development stage and may be a way you can re-bond in a positive way.
Hang in there Mama. It sounds like you have gone through a hard time. Make sure you are taking time to refuel yourself too!