I don't know why they told you to dance with a guy. I will offer this. At college parties where many prospects are,my sisters and I have never told anyone to do anything, but we carefully observe how people carry on at affairs. Why? For instance, one girl who had expressed interest was seen dancing on top of a guy laying on the floor. Every one was agast and the guys called her some not so nice names. After we saw how she carried on for the rest of the night with every guy that approached her for a "dirty dance" we knew she would not be representative of the ideals of our sorority. They may have wanted to see how you carried yourself, who knows.