Bride demanding money as boy called off wedding after engagement

Sir, we and also bride's family are well respected Hindus. My son, a software engineer, after arranged meet with girl, has consented us to proceed with simple marriage. Engagement, treated as half-marriage here, is over with full religious gaiety. Both were working in a same place & use to meet each other & my son says that all meetings ended in arguments, and hence intends to cancel the marriage. He foresees this marriage ends in divorce, which can be averted now. They extinguished fire mutually then and there. He never consulted elders & girl & took decision unilaterally now. Girl says that it is not an issue & she is mentally prepared to live with him, forgetting the bitter treatment matted to her. Son is stubborn & I refused to accept this silly reason. No other reasons. Both are equally qualified. Now the girl's family intends legal recourse for financial loss & loss of reputation etc. Marriage hall, catering, priest etc are arranged. Financially we are not sound. Pleas guide us.