How Honest Is Honest?

I feel like I am an honest person. But sometimes the boundaries get blurred. How honest is honest? If a friend asks me how she looks in a dress, should I tell her that she looks like a whale being squeezed into a baby leotard? Of course I know I should say everything in love. So that doesn't seem very loving. But then, Jesus called the Pharisees a "brood of vipers" and such. That doesn't sound very nice! Don't lecture me, I know He's God and knew what He was doing, yada, yada... But still. Rahab lied to the soldiers to save the spies. That wasn't honest. But yet, she is exalted in Hebrews for that.

I have the "nice" syndrom. You know, "If you can't say anything nice then don't say anything at all". Now, I don't always live by that, but it does clatter around in my head. So when someone hurts my feelings, I tend to struggle through confronting them. Instead of telling them they were rude and hurt my feelings, I tend to pull away from the relationship (at least for a little while).

I have a friend that is amazingly willing to speak her thoughts no matter who is around or what opposite opinions they may possess. She doesn't seem daunted in the least if someone disagrees with her. She listens and answers accordingly. Sometimes her opinion will change but if it doesn't, she is not afraid to say so and even enter a debate. If someone asks her to do something and she doesn't want to, she says no. Says no? With no explaination? Is that allowed? If someone hurts her feelings she addresses it on the spot. I have the greatest respect for this person because she can do what I cannot; be direct and not be ashamed of it. No apologies. She says what she means. Is that okay? Isn't there some line that shouldn't be crossed? I'm having trouble knowing where that line should be.

So I'm asking, how honest is honest?