Chances are that Customer will be back, she knows of your attempt at helping her!!
Its when you see the disenterest thats irritating (or to me) as long as they see you are making a firm attempt to assist no one gets too shook... I worked retail, one of the nicest things remembered came from a customer one day, line was backed up, who knows what else was going on... apoligizing, to customers when they got to register, one customer mentioned that she used to be a demanding customer then went to work for one of the large chains one xmas, said her whole way of looking at things were different now!! Now if I get a little frusteated have to remind myself of those instances and try to be a good customer, challenge myself to make the clerk have a good day !!! :)
Keep up the Good Work all you can do is your best !!