How was I supposed to know she wanted to meet me?

I went on a first date with a girl recently, things went well and we had a much longer date than I expected, plenty of drinking and talking.

I wasn't too sure if she was fully feeling vibe by the end of it but thought screw it, the best way to find out is try to meet again.

So I asked her out again to which she told me "Sorry, I already have plans that day".

Instead of being a pest and for my own self respect, I just decided to take it gracefully and told her "Ah, that's a shame but it's okay :)"

I made plans with my friends to go drinking that day instead and we had a blast, I uploaded some photos to my instagram story and immediately she sees it and asks me "That looked so fun! How come you didn't ask me to go?"

I was under the impression "I'm busy" with no alternative being suggested generally is a soft way of saying no. How would I know it isn't?

How was I supposed to know she wanted to meet me?
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