My big and I were pretty close during my freshman/sophomore years, then we kind of grew apart. We haven't been in touch since she graduated.
One of my pledge sisters was a bridesmaid in my wedding. I haven't heard from her in a couple of years... she just dropped off the face of the planet.
On the other hand, there are a few sisters to whom I wasn't really close during my freshman/sophomore years, who are now among my best friends.
People change.