What should I do regarding my sister's friend who loves me and is waiting for me to marry her, given my family's objection to her as unsuitable and stubborn, with three years remaining until my graduation?

As long as you are unable to marry, do not occupy yourself with a specific girl. Instead, turn to what benefits you in your religion and worldly life until you become capable of marriage. Until marriage takes place, you must adhere to the limits set by Allah and avoid emotional relationships between young men and women, as they are a gateway to temptation and a means to corruption.