Business Etiquette

Last weekend at a conference....
I go to the bathroom in between sessions. After exiting the stall I walk around the hall to the sink. It is at this point I see a woman whom I had interacted with the day prior but did not officially meet.
We smiled.
Paused.
Recognized. 
We made standard girl remarks.
"Hiiiii..." "Hi!""We met briefly yesterday" "Right right""Yes, at the..""Of course""Nice to see you."
We practically talk over each other as our comments of recognition bounce back and forth...finishing each others overly-enthused statements.
Then....
In slow motion she reaches out her right hand....
(said in deep, monotone, robotic voice) "Hiiiiiii..myyyyyy naaaamme iiis Breeee.."
Pause. Pause. Pause.
What do I do here?  
I have not washed.
She's going to remember I have not washed the second our hands shake.
I never want to meet someone in the bathroom ever again.
I've paused too long. My thinking is not fast enough.
I don't know what to do,  it's about to get awkward!
I live my right hand up slowly near eye level.
I look at it.
Mouth the words "I......" (With not wanting to claim myself as unsanitary out loud, I finish the statement in my mind: have not washed)
Then I look at the sink.
"Ha." I say.
"Oh." she says.
She snaps the conversation closed, "Okay well I'll catch up with you later."
I wash my hands. Shaking my head...  
Sigh, I'm forever going to be known as dirty-hands.

Hmph...I hadn't even peed on them.