Girls, What does it mean when a girl touches my chest? What does this relate to?

We've known each other since.3rd grade were in 11th grade now. She just barely started hanging out with me and my friends in the beginning of the school year. She got close to all my friends but got even closer to me. She always gives me a hug every morning than every night she'll give me a hug again and say "see you tomorrow". Than she'll put her hand on my chest I never noticed this until my friends pointed this out to me. I tried asking her about it but she got shy and said its a habit but she never does that to anyone else.
Girls, What does it mean when a girl touches my chest? What does this relate to?
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