Replying to Kind of sketched out, advice would be nice.

So tonight I will be driving my girlfriends little sister and hour a way's to her boy house. What bothers me is that she is 17 years old and this guy is 19... for me it just seems creepy that some one who could easily go to a bar and pick up a loose girl is going after high school girls. If I tell my lady that i refuse to driver her then she just will and ill have to deal with a pissy girlfriend for the night and I don't want her alone in the car with a strange man. But it just seems wrong to drive her so far out and leaver her there with some guy I haven't met and got to know yet. First impressions mean nothing I mean ted bundy gave a great first impression. Am I over reacting? is it normal of guys this age to date girls of that age. Something just does not seem right. Any advice? If my spelling or grammar is bad I am sorry, I just failed a grammar test today so its clear I have a retardation with writing.