well if you're thinking she's not cheating on you... and you truly believe that she's not ready for a relationship right now... this is what you should do.
1) if she has lots of pressures and things to worry about right now, do your best as a very good friend, and support her. I know this may be very hard for you because you still like her very much --but try your best!
2) you can still date other girls if you want. But in a girl's point of view, we think that if you truly like her, you will wait for her until she is ready and not date other girls. This shows that you don't jump into a relationship w/ whomever available, and your feelings are real. Also, what if you're in another relationship, and she's ready? What do you do? Therefore, dating other girls is not an option that I would suggest
3) if being around your ex is that hard... hang out more with your friends, and do other things to get your mind off her!
But keep this in mind, you guys have a relationship... but she's just not mentally and/or emotionally ready for a close relationship right now. You can still care for her without being physically close! Let her know you care thru e-mails, phone calls, chatting, etc. Give her a sense of security, yet give her some space (in reference w/ you being the jealous boyfriend).
Just a question... are her friends guys or girls? the people she was hugging? If girls, there is no reason why you should be jealous!
Being in a relationship, loving her, doesn't mean you own her! Perhaps you're expecting a lot from this relationship that she's not ready for? Perhaps this is the reason she wants some living space for herself...
Since you guys are in this stage... just be patient. Take a deep breathe, and just enjoy your time with her as friends. It may take awhile for her to be ready, since she may want to concentrate and do well in school and get into college. When you do end back up together, remember to give her some space too! She has her own life and her own circle of friends! Love does not mean possession! Some girls like jealous boyfriends... some don't!