How do I deal with a friend who has changed and no longer cares about our affection and companionship after completing her higher education?

Friendship and love between Muslims are a great objective for which a person is rewarded if they observe the Shariah, by accompanying the good and pious; as the Prophet, peace and blessings be upon him, said: "A person is on the religion of his intimate friend, so let each of you look at whom he befriends," and because of the influence of companionship, as he said: "The example of a good companion and a bad companion is like that of the seller of musk and the blower of the bellows."

If the friend is characterized by religiosity and good character, then the relationship should be preserved by seeking out the causes of estrangement and removing them. If she is otherwise, then thank your Lord that He has rid you of her.