Did I Do Something Wrong?

We have this regular customer that comes into the store.
A grandma aged lady who I interact with almost every time she comes in because we save the eggs our birds lay for her so that she can dry them and then give them to schools/museums and such for learning and the like. 

Unfortunately, I didn't have any eggs for her today. 
But I'd gone into the back to double check, and when I came back to tell her no we didn't have any, she kept the door open, effectively blocking both of us from the view of the register.

And she leaned in. 
Asking me.
"Did I do something wrong?" 

O.o Huh? She hadn't done anything out of the ordinary yet. I mean...besides holding open the door to the back room where customers shouldn't be. But...that wouldn't equate with wrong as I hadn't said anything.

She then continued.
"I was at the register, paying for my food." 
-She had a large bag of food in her cart, as well as a single plastic cup of dog food in a bag.
"And I just picked up this container." She pulled the plastic cup of dog food out of the bag.

And I'd halfway been expecting her to say that she actually hadn't paid for it and was it wrong of her to take it, to which I would have been like yes? 
"And while the cashier was ringing up my order I placed tossed it in the bag." 
So I was like...had the cashier not had the opportunity to ring it up? 

"And the cashier was like. >.> Ma'am. I can bag that up for you." 
She said it in a way that was just borderline rude. So it made it sound like the cashier had been like. "Don't do my job! I can bag up the items for you! Don't touch your things! Don't bag things yourself!" 

To which she then gave me the puppy dog eyes and was like. "Did I do something wrong?" 

*exhales* 
"No, no you did not." I reassured her. "You're fine." 

It's not like I could say "Yah, that cashier sometimes rubs customers the wrong way." to the customer. As I didn't want to talk bad about my cashier. As that particular cashier...has their good days and bad days when interacting with people.

*exhales*
I don't know if I convinced her that she was okay, trying to bag her own items. 

Honestly, I felt like she'd been traumatized by the experience. 
Y_Y which I feel for her. I mean...she's a regular customer, it's probably really disconcerting to be 'snapped' at. 

Hopefully next time she comes in, she has a better experience at the register with the cashier.
Though it wouldn't surprise me if she tries to avoid being helped by that particular cashier next time. 

-Sarnic Dirchi