Foursquare Addict

My sister is now as addicted as I am at Foursquare. It's an app that you download on your smart phone and it tells your friends and family where your exact location is when you check in. You also get points every time you check in to a place and these points put your rank higher. My sister saw me logging in at different places and she asked me about it. Well, now her rank is higher than me and she tells me that she loves the app so much. This is where she discovered Madison Avenue Mall; now her favorite place to shop. I see her logging in to this mall almost daily. I wonder what she buys there?