Is there a reason why a girl wouldn’t add someone they like back on instagram?

Long story short I ask my gym crush her name and instagram she typed it on my phone click request. Never added me back told her hit me up in gym. This girl with out question like me. Follows me around gym m, stairs at me, stairs at me when I’m not looking, constantly is on the side of me. I haven’t talk to her since only talking to her 2 months ago for the IG. I’m going talk to her. But just curious why wouldn’t she add me back. Obvious one is she gots a boyfriend (then why type it on my phone)
Is there a reason why a girl wouldn’t add someone they like back on instagram?
Post Opinion