Writing Recommendations for sororities you aren't a member of?

[KDShan]

I have several young ladies who work for me that are leaving for college in a few weeks. They have expressed an interest in Greek Life at their new schools, and I have told them to keep an open mind about rush and to go where their heart tells them. Unfortunately, none of the schools they are attending have a Kappa Delta chapter, so I won't have the privilidge (yes I would consider it a privilidge) to have any of these great young ladies become my sister. However, I think that they would be a great asset to any chapter.
What I am wondering is, is there a NPC reference form? KD has a reference form to fill out on a rushee, and I'm sure other sororities do as well. Would it be ok to write a letter to each chapter on campus telling them what a great girl she is? Would it just get thrown out because I'm not a sister of that sorority? I just believe so strongly in a few of these women, and I KNOW they owuld be great! I'd appreciate any advice!