thank you for the precision. in fact I was just looking at pictures of jobs and I had a picture of a sales assistant. I realised I wasn't able to describe that job more precisely than "sales assistant".
In fact can "saleswoman" be used for clothes --> clothes saleswoman?
"Shoe salesman" certainly sounds normal in AE (see "Death of a Salesman"), and I agree that "saleswoman" and "salesperson" are beginning to get cumbersome. "She is a clerk in shoe store" would work. In my neck of the woods "shop assistant" would be found, say, in a machine shop, lowish in the hierarchy.