I need help talking to this girl I like

I have this huge crush on this girl that ive never even talked to before. I want to know how to get in but I only have 1 class with her. I tried to follow her Instagram but she didnt accept my follow request, and she follows some of my other friends and I need to know how to talk to her. I want to get to know her and I want her phone number but every time I see her I freeze and my heart starts to pound, I need advice. I have no wingmen at the school I go to so its all of my own. There is this one girl that likes me that my crush follows but I dont know if I should go through her to talk to me crush. I dont know if hurting someone in order for me to get what I want is worth it. Any advice?