YABVU if the issue here is carrier bags not the actual rudeness.
What did she actually say? Most people I see in supermarkets don't bring their own bags in Waitrose, never mind Asda etc. I have to restrain myself from lecturing them myself!
I feel brilliant about using strong, permanent bags (ie cotton, nylon etc, not hessian as I don't like it) as these are so much more practical and you can get tons in them. Also, it's much easier to carry a heavy load in a sturdy bag that goes over your shoulders - I couldn't go back to doubling up placcy bags and having them dig agonisingly into my hands etc.
I have a bag my sister bought me called 'Envirosax', it's made of thin nylon, weighs pretty much nothing, and rolls up like a very small sleeping bag with a popper to stop it taking up space. It's absolutely brilliant. I can get loads of heavy stuff in it and it lived permanently in my handbag so I don't have to 'remember' it any more then I need to remember my mobile phone or lipbalm.
I grew up with a mum who always took bags to the supermarket (and a gran who used a basket or trolley) - if you know you're going there then it's hardly rocket science to know you will need bags is it? You wouldn't go swimming and roll your eyes at the thought of having to remember your swimming costume.
I personally think that shops in the UK haven't gone far enough with the bag ban. Most shop still give them away without even asking if you need one. None of them want to 'go first' with a proper ban/ tax.
As for this idea that none of us should bother about the environment becuase it's somebody else's problem (China, USA, supermarket bosses) I despair. What an absolute cop out.
Let's just hand our kids a filthy, rubbish filled world because we don't feel any personal responsibility for it. Let them and their kids sort it out in the future eh.
All this sniping 'yes but what about the clothes bags' 'yes but what about the banana packet' 'yes but what about the petrol' etc is just excuses - we have to start somewhere. Climate change is happening - moaning about unfairness is neither here nor there.