Take it from a teen pov. I'm 19 and had "boyfriends" in jr. high...nothing to worry about. Freshman year boyfriend can be a little more serious, but i agree with the space issue. Just make sure you talk to her, but don't be pushy cuz its embarassing, trust me. Don't assume things; like if she is upset or any change in mood, don't go up and ask her if its because of him. The important thing is that she doesn't change for him. I wouldn't worry too much, in highschool the real relationships were senior year, there were few couples in my school that had stuck it out all four years and so on. So it shouldn't get too intense. Just don't treat her any differently, and if it doesnt work out....well thats gonna be a whole other post....i'm the queen of handling highschool heart ache, i am after all a member of the Dawson's Creek Generation!
But you should also be very excited for her, because if hes a good guy and she's happy, its a great feeling! Who doesn't miss the exciting and innocent feeling of new puppy love like that!? man now i'm jealous!