rec letters

Are only alumnae allowed to write recommendation letters? Or can current sisters in another chapter also do them? Also, are they beneficial to have at USF? I know that at some southern schools they're super important. I'm kind of asking this specifically about ADPi but I'm sure it's the same for all sororities at USF. Please don't bash me for mentioning ADPi, literally any time any one posts on here about them it's negative and rude which is pretty rediciulous...and I just want advice about the rec letters. Thanks!