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How to tell if a girl has a crush on you
Try to catch her staring at you.
This one is a giveaway. If you look across the room in class or at a party and catch her looking right at you, then she may have a crush on you.
If she sees that you've noticed her staring and looks away and blushes, or gives you a little smile, then she may be acknowledging that she may like you. Just don't be too obvious about trying to catch her staring at you, or she may think that you're the one staring at her.