Why do people feel the need to put someone else down when they are vulnerable. My so call friend had…

Why do people feel the need to put someone else down when they are vulnerable. My so call friend had a wine cooler and I said that's my favorite wine cooler. Her response was too bad you should had kept your legs close. It took a lot of self control not to go off on her. But I'm living in house temporary and I don't have no where to go.