DEAR MISS MANNERS: I am a mom of four teenagers, and so am at the grocery store quite frequently. The hardworking employees who try to balance the number of people in line often ask me to go to the express line even if I have a few too many items. I have had to start telling them no, I will not, because so many people have been openly nasty to me about having too many items to qualify for the express line. It is even worse when people glare without saying anything. No one should assume the worst about their fellow shoppers. GENTLE READER: As you and Miss Manners both understand, the employee’s…