<human>: My 20 year old sister just got engaged this weekend to a 20 year old guy whom I've never met. They've known each other for less than a year - most of which has been long distance due to him being in the military and he has been stationed across the USA. She is reckless, rebellious, and immature; but she's also an intelligent, passionate, and caring individual. Unfortunately she has never moved away from home, has never been financially independent, and still has yet to "grow up" (in my opinion) - and while you may not need these things to be in love and get married, they are things I wish my sister would have before embarking on marriage. 

In my honest opinion, she is young, lustful, and still in the honeymoon phase of her first "real relationship", and that is what scares me. But it also scares me that I do not know the man who has asked for her hand in marriage and what his true intentions are. I know it is not my place to change her mind or discourage her from this engagement; however, as her older brother I want to pass on as much meaningful advice as possible. I am seeking advice on how to approach her regarding my concerns while not being overbearing and negative - I realize this is not my life, it is hers. So, any help on how to speak to my younger sister about an engagement of which I don't necessarily approve?

Can you provide a brief overview of the text?
<bot>: My sister is young/immature and got engaged to a man she's known for less than a year and I still have yet to meet him. How do I talk to her about an engagement of which I don't necessarily approve?