Sex and vibrators are entirely different things, the same way that a boyfriend shouldn't have to worry about being 'replaced' by a vibrator. Sex is about the emotional attachment and thrill of being connected with another warm, living human being. Vibrators are there to relieve stress.
I feel like if you get a chance to know what you like and don't like, you can give your partner better direction when the time does come. If you figure out if you like internal or external stimulation you can ask them to spend more time fingering or performing oral as foreplay.
The whole point of giving a young person a vibrator is because sex ISN'T about orgasms, and they shouldn't be having sex just to have an orgasm. If they can give themselves orgasms, they have less stress to have sex with someone, and they have more drive to have sex for the right reasons. (Not that sex for an orgasm is a WRONG reason for some people, but it's generally assumed that you should also only have sex with people you trust, love, and have an emotional investment in.)
Now none of this means that either you or your friends are right, this is just how I see it. If you don't want to give your underage daughter a vibrator NO ONE can tell you that you're wrong, but if you do decide to I think it will only be beneficial to her emotional and physical health later on. Best of luck!