my frnds father wnts her to get married to her cousin n he dont wnt her to refuse for dis marriage coz he says that in islamit is said that shoudlnot say no to tha first proporsal otherwise allah will send lanat on the girls is this true if yes i want to know in whcich surah n ayat it is there ?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Claiming that it is not permissible for a girl to refuse the first person who proposes to marry her and that she will be cursed by Allaah if she does so; all this is incorrect. Rather, the most preponderant opinion of the scholars is that a guardian is not permitted to oblige an adult virgin woman who has a sound reasoning to marry with someone whom she does not like. If her guardian marries her off without her consent, then she has the right either to continue this marriage or to invalidate it. For more benefit, please refer to Fataawa 92711 and 90809.

There is no doubt that if this girl can be kind and dutiful to her father by marrying her cousin provided she is not harmed by doing so, then this is good for her. The Prophet said: "The pleasure of Allaah is attained by pleasing parents." [At-Tirmithi]   

Allaah Knows best.