Too young

What are your guys opinions on having sex at an earlier age. My friend wants to have sex with her boyfriend of 4 months. she’s 15 and on birth control. He’s only one year older then her. She isn’t sure weather she wants to wait till she’s at least turns 16 or not. She’s been asking me if I think she’s too young ( not that my input would shape her decision) and I was just wondering what you guys thought about the whole situation.