Christian Speculative Fiction discussion

Gibbie, Donal, and Ginevra are grown up and now shaping their future lives. Each one has become a much more complicated character while still each being very good. The thread of romance has spoiled their friendship at this point in the book. I had once heard that a young man and young woman can't stay friends without either growing distant or falling in love. What do you think? Can friendships like this survive adulthood in real life?