Re: do u think a relationship will interfere with you hsc?
I started a relationship around this time last year when both my bf and I were doing our HSC. It won't interrupt your studies if you don't let it. Just learn how to manage your time and exercise a little self control. If, however, you're not so good at the self discipline, don't go for it. My bf got higher than his target UAI so we were all very pleased about that. I did alright, but I wasn't too great at self discipline.
Either way, the girl you like knows herself better than you do, so perhaps just let her know how you feel and try to work out an agreement between the two of you. Also, reassure her witht he fact that she still has a year where she's allowed to screw up whereas you don't.
If your relationship survives the HSC, congratulations; it's a huge milestone and it means that you've really got a good thing going on.