Here's my take, I am not a lawyer.
To the best of my knowledge, the term "brandishing" is not defined in any Washington state law. As others have posted, look at RCW 9.41.270 and if you have any further questions, contact a lawyer for solid answers.
If I'm at my own house, on my own property, and someone asks to see my gun... assuming it's a person I trust... I'm at home so I have no problem showing it to them. I'm on private property where I live! If it leaves the holster, it's gonna be pointed in a safe direction and, obviously, body language won't be showing any sort of threatening gestures or mood. Think: Two guys shooting the breeze (no pun intended) and talking about a piece of steel vs. one guy getting all hyped up and the other looking like he needs to change his pants. In my opinion, intent is a huge factor in the legal situation. In my neighborhood most of my neighbors are law abiding gun owners and don't blink twice at the sight of a gun in a neighbor's hands. If I were in a neighborhood where the neighbors didn't like guns, or were unfamiliar with the sight of them, I'd bring the person inside first, and then show it to them.
However, if I were out in public and someone asked to see my gun, I'd say "Well, it's right there in the holster so look with your eyes all you want! I won't unholster it though. Only at the range or at home when I'm cleaning, inspecting or putting it away, or if I need it as an absolute last resort to save my own life, or that of a friend or family member."
Your house, your discretion I say. When out in public, though, I wouldn't unholster it unless you're at a range or you're defending yourself in accordance with the law. It all boils down to common sense, really.
We could all go into "Well what if <insert situation here> happened?" There's millions of different things that could happen. Personally, if I'm practicing common sense, not doing anything unsafe (i.e. stupid) and I'm not breaking the law, then I'm not going to worry too much.
If you're really worried about all the "what-ifs" then just go inside and show your friend your gun. Safely, of course.