Me or Sainsburys staff member?

[HouseofSkullduggery]

My local Sainsburys is in a shopping centre with chargeable parking. You usually have to spend £10 or more to get free parking unless you are also using the pharmacy or Argos which is also inside.
So this morning I had to return some items to Argos that I bought yesterday. I did that no problem and never asked them to validate the ticket as I had a few other things to get from Sainsburys and thought it's quicker to go to the self service tills and do it myself.
I bought items which were just over £7. Paid and started to walk to the machine to validate my ticket. The staff member immediately saw me approaching and stood blocking the machine. She actually had to walk backwards to make sure I didn't go round her.
She then said have you spent £10? Where's your receipt? In a really snotty tone. I explained I'd just been to Argos too but needed other things hence why I was there. But no that wasn't good enough. She said no I would have to pay to park because I hadn't spent the £10.
She was really off and I felt like a naughty child! I just said again I'd been to Argos, I was in a rush and as it made no difference to her please could I use the machine on this occasion. But no she wouldn't back down.
I left and just felt quite bewildered at her attitude. Nobody normally mans the machine. I go in there all the time. Never had any issue. Even going through the normal tills staff have been happy to validate the ticket as long as youve bought something. I feel she was rude and a jobsworth. Aibu?

@SD1978

And everyone saying (shouting) that she's been to Argos- she didn't validate in Argos as you're supposed to- so how was the staff member at Sainsbury supposed to know?!?! Validate in Argos and there would have been no issue.

Not only that but she took something back to Argos so was worse than a customer. The very opposite of what they want. Op trot back there tomorrow and give the poor shop assistant a bunch of flowers and apologise. Call the manager indeed!

Customers are always rude to the staff if they have been caught out by not adhering to the requirements, it’s never there fault. I work in a industry which by law forbids anyone entering the area under 18 yrs,& strictly no pushchair or proms. We have a 6ft sign at the area entrance & a voice tells people the area is forbidden to under 18s. Person enters with a child, & I have to inform them of the law, immediately I’m told to go screw my self, as the child is only watching,& not doing any harm, I have been threatened many times, verbally & with a screwdriver. No problem it’s all on camera so it doesn’t bother me, the thing is, they have to walk past the six foot poster, & then hear the recording,but still choose to ignore, we can lose our licence & face prison through there idiocy & it all has to be logged on a tablet. My point to this is that, the authorities send unknown persons to us, to see if we are adhering to the law, & that’s what has happened here, the op did Not meet the criteria, but they always winge when caught

Her job wasn't just to monitor the machine

Her job obviously is to monitor the machine . You are making yourself skyns ridiculous now.