Friends 'Til the End : Pinned?

I've watched this movie many times and I'm always confused on the part where the sorority girls are all sitting on the floor with candles and Suzanne blows hers out first and the girl says "I'm the one who just got pinned!" What does this mean?

sincerely written from my brother's blood machine

Its a thing when your boyfriend is in a fraternity. its bascially a promise for engagement. In some fraternities when a woman is pinned she can know the fraternity secrets, etc.

Additionally, sororities have a ritual where a candle is passed around for a sister who has gotten lavaliered (getting a necklace with her boyfriend's fraternity letters, indicates serious relationship), pinned (given her boyfriend's fraternity pin, even more serious), promised (with, you know, a promise ring), or engaged. Usually, the first pass of the candle is simply for sisterhood, and then the other categories are listed. The girl with the honor blows out the candle.