Is it permissible for a girl to marry with money that is a mixture of lawful funds and bank interest, and does the sin fall upon her or upon her father?

There is no harm for a girl to take mixed money from her father to prepare herself for marriage, as it is permissible to deal with mixed money and to accept a gift from it, especially if the lawful portion is greater. The father must dispose of the unlawful portion of his money by giving it to the poor and needy or for general Muslim welfare, and he is permitted to take from it according to his need if he is poor.