Engaged at 17?

A close family friend of mine recently got engaged to her 20 year old boyfriend of 1 year. She doesn’t actually know that I know yet (we’re meeting for dinner tomorrow). I know that she is going to want to share her excitement with me and ask me for advice and whatnot, as I am engaged myself. But the difference is, she’s 17… I’m turning 22 this year – and my wedding isn’t until 2015. My fiance and I have been together a long time and we both have careers and a steady income. She is in grade 12, she has a part time job but she has no plans on going to college because her fiance is in a band and has plans to “make it big”. They are planning to get married in July 2014 after her high school graduation. I wanted to ask this question on here to see what other people’s thoughts are on this matter. I am NOT excited for her. At all. I have know this girl for ever and I love her dearly. She is very immature. She is a kid. I am dreading our meeting tomorrow because I’m not sure I can hide my feelings…. I feel like I should express my concerns because I really don’t think it will work out and I don’t want to see her heartbroken. It’s her first relationship. But is it my place?