Why did some random little girl give me a nasty stare for no reason?

I went with my grandma to her doctor's appointment I went inside the building and got in line and I felt many stares and I looked around and saw two little girls infront of me with there dad and they kept looking me down and observing me they were probably like 10 and I just looked at them because I was starting to get annoyed with the staring. After my grandma signed in we sat down and i was looking around and i saw the same little girl infront of me with her head turned looking at me with the nastiest stare. I was so confused because I don’t even know her or did anything to her. She kept turning her head to stare at me and the other little girl that is probably her sister wasn’t even paying attention she was minding her business I also noticed that after she was giving other people ugly looks too. But I don’t know why she was acting that way towards me?

Why did some random little girl give me a nasty stare for no reason?
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