Nosa, don't worry about it too much. It's 77 days till the HSC. People are stressed. I understand how it feels to have a boyfriend at this time, and as long as you're there for each other, you'll make it through.
There's nothing wrong with her talking to her friends. Don't cause any fights by taking it the wrong way. You should also be concentrating on your studies, no matter how confident you are. Let her have the space you want, and take advantage of your own space. Help her and be there for her when necessary, but don't make her feel pressure from two sources.
LOL, my dad's in the other room giving his friend love advice.