To answer the original question...not too sure about DG's policy....but I am pretty sure that it is for Alumnae only.
http://www.deltagamma.org/resource/reports/sponsor.pdf
According to the form, the first page says "(to be used by members of Delta Gamma only)" (no mention of Collegian or Alumnae specific'ness).
But then on the second page, at the end, it says:
"Please clip and send to
alumnae immediately after recruitment!" which leads me to believe that alumnae only can write recs. This probably so that this practice is not abused, etc.