My mother stepped back- now not accepting my love

I am an Assamese girl and the boy i love and want to marry is Bengali. Although my mother said that if i chose a boy for me and he is bengali other than assamese she wil not have any problem . bit the day I revealed to her about my love she strictly said no to it and told that bengalis are different from us and i will not be able to survive with them. She denied to everything that she told earlier and now i a in dillemma. She;s a bit arrogant and doesnot want to even have wordings with my boyfriend. I know if she has then definitely he can impress her but she s not at all ready to even listen to me. How to handle this situtaion. Please suggest.