First a warning: Never challenge a stall. By asking her to give a reason when she says she has none, you are in essence calling her a liar. It’s like you do not believe she is uncertain. While stalls are frustrating, when challenging a stall, you create unnecessary conflict. Never say, “What’s to think about?” or “What do you mean you want to think about it?” or “What exactly do you want to think over.” When she says, “I want to think it over,” it implies she is uncertain. If you force her to invent a reason, it will incline her to defend it. She gave you no reason for not buying, so do not force her to come up with one. We want to avoid conflict, especially when we are trying to gain commitment. We want to use persuasion, not pressure.