depending on when you interview, a school can offer an acceptance anytime between october or so all the way through the beginning of classes, depending on the school (yes, that's a time span of nearly a year). if you're on the waitlist, then you may get an acceptance if and when a spot opens up for you. there's often a lot of movement on waitlists throughout the summer because people who are holding multiple acceptances are *technically* forced to pick one school by the middle of may. thus, a bunch of other available spots open up, and people are sequentially pulled off waitlists and given acceptances, which they can accept or reject if they have an acceptance somewhere else that they'd rather keep. this keeps going until a class fills up all of its available spots.
so it doesn't mean that phillybabe's application wasn't reviewed until now--it means that a spot finally opened up for her. she can withdraw from other schools at any time...and then that school offers her spot to the next person on the waiting list. and so it goes. nerve-wracking, isn't it?