Be more worried about earning great grades in high school. Volunteer and do some good. Get involved in clubs or sports or other activities. Worry about all that before sorority "reputations" which depend on rumor and outright lies.
While you're doing all that, you (and your mom) can be asking around among your friends - older and your age - to find out who is a sorority alumna. Keep a list of who is, and what their sorority is, so that you can later ask them to write you a recommendation.
Work hard, and best of luck!
