Well, it's a funny old world, and I suppose that, despite not agreeing with the extreme vegetarian/vegan view of the world, I can accept that the lady (who I am sure is not alone in this conviction) is entitled to her opinion and her stance. Well, almost, since the five pound notes are in fact legal tender and therefore should by law be accepted as a means of exchange. But that's a piffling matter, really. There are two bigger issues here for me.
First, there's the matter of vegetarianism itself. I don't have particularly passionate beliefs about the rights or wrongs of eating meat, but it seems to me to be a fairly obvious point that our bodies have evolved to survive on an omnivorous diet, and although I frequently enjoy meat-free meals, I also have no problem eating locally-sourced and ethically-raised meat products. On this subject, I agree to politely disagree with folks who find themselves standing atop a pillar of righteousness. Figuratively speaking, I may from time to time fire little paper pellets at their ankles, but that's about as far as I can be bothered to go. Leave me alone with my food choices, and I'll leave you alone with yours.
The second point concerns the question of making a stand against perceived evils. As our society evolves and we all (at least in principle) have access to enormous and unprecedented amounts of information, we learn more and more about our world. I doubt, for example, whether fifty years ago - or even fewer - anyone would have been privy to the information concerning the involvement of animal products in the production of bills of exchange. It's the kind of intriguing detail that is now openly available to the public. Which makes me wonder: how many things can people protest about/take a stand upon before life becomes too awkward to navigate?
I wonder, for example, whether the bricks which were made to construct the Victorian buildings within which the vegetarian cafe stands, were made using child labour (almost certainly the case)? If so, is it ethical to make use of a building constructed using such methods? Should the cafe serve people who admit to using diesel vehicles (thus causing rather nasty polluting particulates to infest the atmosphere shared by animals and humans alike)? Do the clothes that customers wear represent a monoculture (cotton, for example) which threatens the habitat of wildlife at home or abroad? Is wine (another monoculture) acceptable?
It's possible to find something 'wrong' with almost anything in our lives if we look hard enough and reason with enough attention to detail that we chase logic down blind alleys. Just getting over an infection, for example, means the 'death' of billions of bacteria - I wonder how that would sit (because I genuinely have no idea) within a Vegan view of the world? I don't have answers for everyone (who does - except of course, Donald John Trump, who is the best at knowing everything, but manages not to be at all bragadocious about it), but I did come across this article as I chased my own thoughts on the matter, and I hope that it may be enlightening. The harder you look, the more you find...and the more you find, the greater is the potential for surprise.