To be honest, I’m tempted to tell you that you should never do this: The woman can get confused. However, if you’re getting tired of your booty call, simply stop texting or calling her. She may get the message and do the same to you. But if she doesn’t, just respond to one of her texts by saying that you’ve been super busy and that the rest of the month is looking crazed. What you’re basically saying is, “I don’t have time to have no-strings-attached sex with you,” which is a polite way of saying, “I don’t even want to have no-strings-attached sex with you.” She should get the message.