Why doesn't she respond?

Okay so long story short I met a girl while I was on the store, walked up to her and started a convo.. it was all good and at anytime she could've walked away but we were both going strong. Anyways I had to go so I asked her for her IG and she gave it to me with no problems.. both talked about hanging out etc.. later that night after looking at her page I DM her a compliment nothing sexual, just a nice compliment but I never got a reply back.

It's been a month now.. she watches all of my IG stories faithfully but never replies to me.

Why do girls do this...
Why doesn't she respond?
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