Each to their own. Maybe that reader you saw has a great need for the kind of protection she recommended, but that doesn't necessarily extend to readers en masse, because it flies in the face of free will. I agree that it is important to be aware of such issues when channelling or participating in spirit work, as Promise said. But Tarot is not spirit work, it uses entirely different energy dynamics.
My idiosyncrasies in this area are: I make sure I set up my reading area
exactly as I like it to be. I place crystals and other objects on and around my cards. I make sure I've eaten enough and that I've got plenty of water on hand (especially at fairs and markets when there's very few breaks). I
never read when I'm sick or highly stressed. When I get tired I make sure I take a break. And if a sitter has an energy lock (my term for someone with an angry demeanour who doesn't resonate with
anything in the cards), I refund their money and explain that it's not possible to give them assistance. All of these things help me to stay grounded and centred, sustain the integrity of my energy field and thereby keep my immune system healthy. I don't project this practice onto anyone else, or judge others for not using the technique I do.
As others here have said, what works for you, works best. Find your own way of keeping yourself safe. Adopting others' methods would just be rote, and therefore, ulimately ineffective!
hx