Having worked in a couple of grocery stores, I can tell you that I had my favorite regular customers. When one of them would come in, it would be one of the best parts of my work day. I may have seemed too happy to see them, or overly helpful when they were in, by contrast with how I treated most customers. Most of them were neutral or they got on my nerves. Sometimes favorite customers were even passed on, as workers came and went and asked the new person to make sure they continued to be treated well. Then again, you never know. Maybe you could ask her what she likes to do when she is away from work.