Is it permissible to give money, known to be unlawful, in charity to my friend for her to buy clothes, after its owner refused to take it back from me, knowing that all of his money is unlawful?

If a person's entire wealth is unlawful (haram), then it is not permissible to deal with him, nor to accept his gift or donation, because it is the very essence of unlawful wealth. Whoever knows that their wealth is unlawful, their giving is forbidden. And whoever doubts it, the cautious approach is to refuse it. You can ask him to purchase items for you on credit, not with his unlawful money, and then pay the price yourself from your own lawful money. If he buys items with his unlawful money and gifts them, it is not permissible to accept them. If you do take them, you can donate their value to charity, and do not return them to him. If your friend is poor, there is no harm in giving them to her.