Girl's Behavior

Why did this group of girls I know stare and then lie about it?

I was sitting at lunch with my friend. I know two out of the three girls in the group and one I have a crush on.

Me and my friend were about to get up for some water and they were all just staring.

I waved over and tried to mouth “what’s wrong” but they just kept looking at us then started laughing.

I asked one of the girls later when I had a chance over Snapchat and she just said “oh we were in a good mood and you were in our line of vision”.

I don’t believe that as one of them turned their head around to see us and they wouldn’t stop looking when we spotted them.
Why did this group of girls I know stare and then lie about it?
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