I was referring to when it starts out good, then eventually becomes less than glorious to God. In such a case would the friendship/relationship be worth salvaging, or should it be avoided all together?
Keeping in mind that there are so many other parameters involved here. If we are talking about a closed environment where nothing else intrudes we can say for the sake of conjecture that it is this or that, but life is not that. The reality is always different than the suggestions we make in analyzing a situation between two people of the opposite sex.
We in truth need to view the relationship to God who is Love. Paul from all accounts never married. Surely he loved and was loved. Yet, the English so limits and interlocks the meaning of this simple/complex a word. Look at the Greek definitions and one can choose how one feels about this other in what we would call friendship and how each in man/woman touches upon each of them. Understanding that one can perceive the friendship in one way, doesn't necessarily mean that the other is of the same mind.
Agape, Phileo, Storge, Eros.
Always, knowing that God sees into our heart and the following scripture is pertinent to the honesty needed in each person.
Beloved, if our heart does not condemn us, we have confidence before God; and whatever we ask we receive from Him, because we keep His commandments and do the things that are pleasing in His sight. 1 John 3:21-22
With the Love of Christ Jesus.