What should a committed young man do who feels he may have tempted his female university colleague with his behavior, knowing that he avoids speaking with girls and fears temptation for himself and for her?

May Allah reward you for avoiding conversation with girls, and remain steadfast in that. Studying in mixed-gender universities is a cause of fitna (trial/discord) and corruption, so you must fear Allah and be cautious. If a non-mixed university becomes available to you, transfer to it. Beware of this girl and her interest in you, lest she becomes a fitna for you. Be keen to associate with righteous people and cooperate with them in beneficial activities, and invite students to beneficial knowledge and righteous deeds. There is no harm in ceasing to attend university for a period if no harm befalls you, as it is a good matter that keeps you away from causes of corruption.