Girls on INSTAGRAM, Why do you follow back when you don't want to talk?

I just don't understand. I followed this girl on Instagram and she followed me back, I texted her and she replied then she stopped replying. I don't text much and I didn't bother. Then I texted her after sometime asking "why follow back when you don't want to talk?" She replied by saying "should I block you then?" I blocked her after that! Recently a girl from school who I follow (who also follows me back) started posting political news. I replied to her story and she put my reply as story. We talked a little and it was okay. She send me a funny post then, then another post, then another. And she doesn't reply when I reply to her posts. I asked her why did she send me and she said that she selected all. I was like wtf. Why do girls do this?
Girls on INSTAGRAM, Why do you follow back when you don't want to talk?
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