Why doesn't she reply to my snapchats?

We are pretty good friends and flirt a good amount but she doesn't reply to my snapchats. We talk usually everyday after class. I am not that big into snapchat, I only send her one maybe once a week or less. Her best friends on snapchat are guys that I don't really ever see her talking to. Why do you think she does this?
Why doesn't she reply to my snapchats?
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