Rude Expectations

I threw this on my fb but not here.

After handing out some food, I close the window.(as per procedure) Talk to my manager. We're not shooting the shit, this is srs bsns. Well sorta. I was asking if I should find a headset.(as per procedure) Even though taking orders and handing out food for me is a bad idea, and my brain was already barely working.
So I check the screen for the next order. Sundae and a cone. Open the window.
"You know, it's rude to have your back to someone" The semi elderly lady in the van says.
"I was talking to my manager" My reply. Figured it would end the conversation there.
"It's still rude."
"We hadn't even initiated conversation yet." My voice isn't mean, or demanding. I'm confused, and soft. I'm not seeing how I was rude at all. Window was closed. We hadn't spoken. Hadn't made eye contact. Doesn't make sense.
"Are you arguing with me?" She says.
"Here's your sundae, and cone." I figure it'd be best to just get her the ice cream. She can't listen to reason because she's an old bitch.
Now she doesn't want that cone, because it was crooked. Yeah, it looked like a witch's hat, but it all goes to the same place. Whatever.
I toss it, and laugh the whole way to the machine. This is just too ridiculous.  I then create what is most likely the best ice cream cone I've ever made.

When I return, guess where this old hag is?
Door open, tending to a kid in the backseat.
WITH HER BACK TO ME

I resist the urge with every fiber of my being to say "Ma'am, it's rude to turn your back to someone"
Oh the freaking irony, is too much!
Instead, "Ma'am, your ice cream is ready." I'm hoping she gets the point.
After a few more seconds, I'm assuming she was giving a kid the sundae, she's back in the driver's seat, takes the cone and is gone, without another word.
 I thank her for her visit.

not sure if I won there...
I'd guess no because you can't win against someone that's irrational.