Back step from engagement

My brother was engaged with a girl last year.and thier family want one year for marriage by saying financial problem.we said ok as we done only roka.( no rings has been exchanged ) only formal meet was happen and roka done by giving few hundred money.in that one year my brother meet that girl thrice and with one member each from both family .she never looks interested or curious about this marriage . even always give excused my phone was theft or i am tired so no time to call .in that time we asked several time to girl's parent if she is doing marriage by her decision or forcefully .they always said she is agreed and she is little but shy thats why dont talk too much. before 20 days of marriage my brother received strange messages on behalf on girl's boyfriend's sister through Instagram.she mentioned that she is my brothers girlfriend and never wanted to marry you she is agreed due to his father ( who says i will die if you dont do this) my brother asked why i believe you . then she send all chats which is happening between them . even she shared those chats also which was happen with my brother.we were shocked and asked thier family members what the hell is this.they said give us some time we will investigate who is he. but we already mentioned that we are not ready for this marriage as their were some messages include of life threatening. . then they come with few people after 3 days and said yes these messages are done by our girl but she was so tense ( ki mere papa kaise shadi karenge itni jaldi kum paiso me) so just to postponed dates she has done the same..everytime you mentioned she is so shy and now giving life threatning so its not understood and by taking life on risk we cant do this marriage .bcoz anything can happen after marriage .then they said we have done mistake please forgive us and dont deny for this marriage .otherwise we will see you in court. we have all chats and recordings what they said and even excepting for these messages .please suggest what we should do .