I really need some help about my friend!

Ok I have this friend and she is still a virgin but she feels the need to please every guy she meats and I think that is a bad idea I don't know how to tell her that. She is a great friend. She is my best friend and the only thing that I am scared about is that she is going to turn out like her other friend who got pregnant at 14 because she felt the need to please every guy that she met. She has low self-esteem but I just don't know how to tell her that can someone please give me some adivce about this.