What does it mean if a girl says she'll get back to you and does?

Anonymous
I asked a girl out, and she told me that she'd get back to me. Usually that means she's not interested, so I assumed it was a no and considering that she ignored me the next time I saw her in person, I pretty much confirmed it was. But then the next day she texted me and acted like we were still on.

How should I take this? Be kinda mad because it doesn't seem like she really wants to go? Or be happy that maybe she discussed it with her friends first? In either case, my interest has plummeted a little because I thought she'd say yes right away and didn't.
What does it mean if a girl says she'll get back to you and does?
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