Girl's Behavior

If she likes me then why didn't she follow me back on instagram?

If she likes me then why didn't she follow me back on instagram? Through the school year, this one girl in my class has always acted flirty towards me. She's always touching me. For example, one time she was putting her hair on me. Another time, our volleyball team was taking a picture together (we are on the same team at our rec center) and she seemed to either bumped into me on accident or purpose and I felt her boobs on me. Other times, she has touched my shoulders and chest. Not only that, but she also has called me bae a few times. She also likes working on classwork with me and being my partner on everything. That fact that she is nicer to me than the other guys, and the fact that she is really touchy has made me believe that she might like me. Today, I followed her instagram and she did not accept my follower request. If she likes me, why didn't she follow me back?
If she likes me then why didn't she follow me back on instagram?
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