Is it permissible for a girl to keep pictures of athletic heroes and political leaders (non-Muslims) on her personal computer out of admiration for them?

It is not permissible to keep pictures. A girl's admiration for non-Muslims is forbidden, based on the words of the Prophet, peace and blessings be upon him: "A person will be with those he loves," and "A person is on the religion of his friend, so let each of you look at whom he befriends." The girl must repent and stop keeping the pictures, and instead replace them with Islamic history, the biography of the Prophet, peace and blessings be upon him, and the lives of the Companions.