Is one-sided love for Allah considered valid, or does it require a reciprocation of feelings from both sides, and what are the signs of reciprocal love for Allah?

Love for the sake of Allah is among the best deeds and the strongest bonds of faith. One of its signs is that it increases with a person's obedience and decreases with their disobedience. Its cause is the servant's love for their Lord, their religion, and their Prophet, and their adherence to His law. If your love for this female doctor stems from this meaning, then you love her for the sake of Allah, and her lack of reciprocation will not harm you. Her lack of reciprocation might be due to your own lack of commitment and steadfastness, because a committed Muslim loves their committed brethren.