It probably doesn't have some huge meaning. Maybe she is just letting him know because he asked her where she was headed. Maybe he is trying to make plans with her and needs to know her schedule. I think it's very petty to try to make someone jealous on purpose, and I don't think a lot of girls would do it. But it's not impossible. On the flip side, she could also be trying to send the signal that she is interested in another guy and not him, or isn't interested in choosing one guy. My advice is to not read into it so much. There's really know way to know how she feels without asking her, and it's just a trip to the park.