Is it permissible to use riba money that has come into my possession to contribute to the construction of a mosque?

If the money is usurious interest, then it is unlawful (haram), and it is not permissible to possess it except for a poor or needy person to the extent of their need. If this condition is not met, then the unlawful money must be disposed of by spending it on general Muslim welfare, such as mosques, or by giving it to the poor and the destitute. The questioner (sister) should advise her friend to withdraw her money from the usurious bank and to repent to Allah.