[pibetaphi2013]

You don't know why they asked you back. And even if she said it was numbers, you were still asked back over other girls who could have been invited. They still wanted you.
Also, I don't think it's right to say the woman who preffed you was disinterested in her sorority. If a pnm came in at pref and told me she had "found a home elsewhere" and was not interested in my chapter, I probably wouldn't try too hard to convince her otherwise.