Helen,
Per the Sigma Alpha Iota CPM, chapters have the privilege of selective membership. Page 12-4 at the bottom of the page under the heading "After the Party" states: "Soon after the party, the chapter will vote on membership or send an invitation to a second recruitment party. The chapter members must be reminded that they have the privilege of selective membership, but they must not abuse the privilege."
Keep in mind that we had 13 girls come out during our rush week and invited 12 to preference. While I cannot go into MS discussions within my chapter, I will tell you that we want women who are respectable, talented, live the standards of SAI and fit well into our chapter.
And, I am so thrilled about our class of 10!