Hate that my best friend calls someone else her best friend?

I know that this might sound childish, but I feel a bit jealous when my best friend calls someone else her best friend. We've been friends since we were kids (over 10 years), and she met the girl she refers to as her best friend a couple of years ago. I know it doesn't matter, but I can't stop feeling left out. So does anyone else feel the same?
Hate that my best friend calls someone else her best friend?
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