L.H.
I'm confused as to when she was adopted- birth? two yrs old? That makes a difference in the advice...
Anyway, I agree with others-- that she may just be overtired. But I would cut her some slack. Like was mentioned before, she is dealing with MAJOR culture shock (if she was old enough to remember). Western culture is the ONLY culture that does not sleep with their children, and this has only been happening for a few hundred years. Thousands of years of evolution cannot catch up with a few hundred years of isolated cultural change.
If she was adopted more recently, she may also be trying to develop trust and intimacy with her new caregiver (as well as dealing with grief and loss family of origin/familiar surroundings). Cuddle time and skin to skin contact is the best way to develop these things (very primally human. she's 2- thats "where she is"). It may be that the fights around bedtime are due to fear or mistrust and lack of control over her personal safety (again, if it was a more recent adoption). Remember, you are most likely having to start over in regards to emotional bonding/development with her. Be patient, firm but caring. I promise-- she will not be 10 and still giving you bedtime troubles. This too shall pass!
A good quick and interesting read for understanding some early human physical/social/emotional development:
"Our Babies, Ourselves"