Tink,
My chapter was (and still is!) full of women who managed to maintain high GPA's and commit to jobs, offices within the organization, and many other activities. I have found that the key to success is to learn about your own abilities and limits and not to push yourself beyond them. Take some time to determine what is most important to you and what you can commit to so that you don't feel like you're stretching yourself too thin. Also, every GLO has scholarship requirements and ways for ensuring that their members meet them, whether they are incentive programs, tutoring programs, study files, etc. And, once you join, there is always someone around to study with.
You should also bring up your concerns during rush to get a feeling about each individual chapter's attitude towards scholarship and employment. Best of luck to you!
~Donielle