In everyday speech, the word "friendship" implies mutual support. One remembers birthdays, celebrates marriages, introduces romantic partners, etc. And yet many of the things a conventional friend would support become meaningless on the Noble Eightfold Path. For example, the Vinaya prohibits matchmaking, which causes one to become entangled in the cravings of others.
Yet a friend is also one who supports one on a spiritual path, providing encouragement when faith lags and self-doubt causes one to flounder and lose hope. Indeed, from SN45.2 we have:
Good friends, companions, and associates are the whole of the spiritual life.
Given that your friend is a "virtuous person, extremely caring, curious spiritually," there would be common ground in discussing the precepts or observances either one of you has taken. And where the understanding of spiritual goals differs, then much fruitful discussion can unfold to benefit both. These conversations will naturally develop as you observe your own precepts. Inevitably, those observances will cause surprise in others you interact with. For example, if you are not eating dinner, then being invited to dinner creates some interesting conversations!
In these conversations, compassion will be critical. One's own understanding of a precept and its observance may only be superficial. Our wisdom grows as we apply the precepts compassionately to our own conduct in relating to others.
Perhaps your friend will become a good spiritual companion and associate.
Another important point is your statement about "not feeling much friendliness". As equanimity and tranquility fill your life, it becomes less driven by pleasant or painful feelings. If your friendship was based on pleasant feelings and shared cravings, then that basis for relationship would naturally vanish. For example, choosing celibacy would drastically change the nature of a relationship.
Examine that "not feeling much friendliness" and ask yourself if there might now be an element of unwholesomeness to formerly enjoyed shared activity. Here, too, compassion is crucial because it is the activity you would avoid, not the human being that is your friend.