How old is she?
My DD is very strong willed...some days she will throw tantrums over every little thing...she went thru the thrashing and throwing herself around stage...she fell once and that stopped that. She still has fits...she hates to get in her carseat so she will scream and fight me...then of course she flips out when i go to take her out of the seat...I think its just part of being a toddler and trying exert your independance. I just walk away from her when its really bad. Also not sure on your situation but Im assuming she is hid child from a previous relationship?
My best friend was in a similar situation and they found out that her mom was telling her stuff about my best friend so of course the kid would act crazy when she came to visit.