How do I confront her?

Ok my niece is 10 and my little sister (17) just sent a screenshot to my phone from my nieces Instagram messages between her and a little boy who I guess is supposed to be her boyfriend. To make it worse the little boy lives on the next street over from my moms (her grandma.)

(My nieces mom (My oldest sister) passed away three years ago and now we are all working to be that motherly figure in my nieces and nephews life)

How do I confront her about the message? How do I punish her? I am just so disappointed.

My first thought was to attempt to kick her head off her shoulders since she wants to give head so badly. WHAT DOES A 10 YEAR OLD KNOW ABOUT GIVING HEAD?! I know I can’t take that approach but I need advice ladies because right now I want to hop in my car, drive to my moms, and kick her little ass 🤦🏽‍♀️

This is my oldest niece so I hold her near and dear to my heart. And I just got her her very own iPhone at the start of this school year. Disappointed is an understatement. This is literally my first “baby girl.”