Oh dear. Not much chance with that one. She really did invent her own space, didn’t she?
For what it’s worth, barriers will let you back out within 5-10 minutes without paying, even in expensive private car parks like NCP or Q-Park. I’ve done it many times before.
As far as the law goes, councils need to put a terms and conditions board in a fairly obvious place, usually next to the entrance or payment machines. Looks like they’ve done that, and you’ve said it mentions parking correctly in a marked space.
Unless you can find a technicality, this is probably one to pay before it doubles. Forget about adjudicators - they only decide whether the contravention occurred or not. They can’t take any mitigating circumstances into account and can’t let you off. As far as they’re concerned, if you broke a rule, you broke a rule. End of story.
At the end of the day, if a car park is full you’re supposed to leave and go somewhere else. The barriers will let you back out if you leave within 5-10 minutes. They have to - in case you can’t find a space or don’t agree with the rates.
A council or an adjudicator won’t accept “parking correctly would have made me late” as a valid argument. Looks like she chanced it and got caught. I’ve done it before - it’s a risk you take. This time it didn’t work out.