Spiritual friend to me means the friendship between the Guru with their students, the sangha community and lay practitioners.
What Buddha Shakyamuni said was "Spiritual friendship is the whole of the spiritual life!". This statement is true as Buddha Shakyamuni had said, that after his passing, he will manifest in many different forms, as whatever being as it need be, to be of benefit to others and show them the way, like spiritual guides, Gurus, reincarnated Lamas, Geshes, beggars, prostitutes, ministers, kings, dharma teachers, holy men and women etc.
When we walk the path of spiritualism, we need support for our body, mind and soul to keep us intact on the path, encourages to walk on, not give up in the midst of obstacles, look ahead, gives us hope, console and comfort us, share with us, forgive and forget. That is the spiritual spirit and friendships are built on these. The path itself was not easy at all but based on friendship, we can all make it at the end. If not in this life, but the next.