60 girls in my new member class and about 200 in my chapter when I was in school. I knew everyone. Was I BFF with them all? Certainly not. But the same would have been true in a group of 30.
FWIW, I really enjoyed being part of a large chapter. Girls came from all different backgrounds and majors, we had a ton of talent to choose from for Homecoming skits and intramural sports, and a lot of different interests represented in various campus activities.