In the video game Ripening Tingle's Balloon Trip of Love, the protagonist Tingle meets a fortune teller who demonstrates her powers to him. She asks him, "You come from a far away town, right?" If Tingle answers, "No", she responds:
うそ おっしゃい ! おばさん わかってるの。
あなた まよっちゃったのよ ・・・
Now, from what I understand,
うそおっしゃい means, "You're lying". However, since she continues with "I understand, you're lost...", it doesn't sound like she really disbelieves.
In this context, is
うそおっしゃい to be taken literally, or is it a set phrase expressing astonishment like, "You must be kidding" ?