they're using you. sorry sweetheart :[

if you want, you could do what others have been suggesting and just take a little weed, or shit tell them you don't have any, see if they still wanna hang with you. if not, then just don't call them or answer their calls. i understand you like one of them, but there are plenty of others chicks out there who will like you for you, and not just the weed.....that's a bonus lol