What is the ruling on selling accessories to unveiled girls at the university, knowing that the money earned from this is spent on charitable deeds?

Selling accessories is permissible in principle. However, if one becomes certain that the buyer will use them to display her adornments in front of non-mahram men, then it is not permissible to sell them to her, because this constitutes cooperation in sin and transgression. The money earned from such a sale is unlawful and cannot be purified by spending it on good deeds, for the Prophet, peace and blessings be upon him, said: "Indeed, Allah is good and accepts only what is good."