[adpiucf]

Depends on the school, but typically once a week there's an event. All of these things are voluntary participation. You should trust her not to cheat on you. She's going to these events to hang out with her sisters-- it's a girls night. Yes, there will be boys there, but they'd be there, too, if she was having a girls night anywhere in public. No sorority makes its members make out with fraternity boys, etc.

Show your support, come around to the house with her, go to events with her, etc. If you are feeling like you're not spending enough time together, communicate that you miss her and tell her that you're making her dinner or doing something romantic.

If it becomes an issue and you feel like you're growing apart, communicate. Either you'll both make the effort to understand or you'll part ways.

Your concerns are common when one member of a relationship is rushing. Don't worry-- you're not the last. Yes, sometimes people break up over this and sometimes it isn't an issue if the couple is committed to one another.

A sorority is a time committment. So is school. So is your relationship. Maybe you should also look into getting involved on campus, either with an intramural sport, fraternity or campus club so you fill your calendar, too.