She's deluding herself if she thinks that she can avoid contact with cold viruses. I was a teacher. I had a certain number of colds every year in spite of washing hands and using antiseptic constantly. We had a dispenser right in the room.
During cold season, the kids, or in the case of store employees, the customers are getting viruses on everything they touch.
In a classroom it is all the materials, papers, walls, doors, doorknobs, books, clothes, furniture, pencil sharpeners, everything.
In a store it is walls, money, furniture, carts, products, shelves, everything.
Every dollar bill or coin she handles is a virus factory.
When I retired from teaching I stopped having colds almost entirely.