Why do you think Amari cried and screamed when she was bought and taken away by Mr Derby in the slave trade?

I think Amari was falling in love with John in the end and I didnt think she would want to leave him. I just dont understand why Mr. Derby would want to take that dream of being with John away from her. And although MC Hammer was dancing in the back of the train, she just didnt feel comfortable like she would have with P. Diddy