Any alumna can write a letter of recommendation for any PNM going through recruitment at a school with a chapter of her sorority. The alum doesn't have to be an alum of that specific chapter. For some NPC sororities, an active member can write a letter of recommendation for a PNM if that PNM is rushing at a different campus.
These days, a lot of people get associate degrees and then transfer in as juniors to save a bit of money, so you most likely won't be alone.
(Yanking IrishLake's chain a bit
Alumna = singular female alum, alumnae = plural female alums. Alumnus = singular male alum, alumni = plural male or mixed-sex alums. I blame 7 years of Latin for doing this to me *sigh*)