Can I sue for slander, defamation of character or atleast get them expelled from school?

A woman from my college asked me repeatedly how far along I was. At first I didn't know what she was talking about then she kept asking. I told her I was not pregnant at least four times. She did this in front of everybody, we had a fire drill and everybody was coming back up stairs. After I told her no and I went back to our clroom (same cl together) I could hear her tell her group of friends over there that she asked me. They were all gossiping about how they didn't believe me and that I was pregnant. They kept talking about is she really that fat? Even though that hurt, this group has been spreading these rumors around school that I'm pregnant. I'm almost done with school and with this rumor going around I'm afraid that it's going to ruin my chances when I go out on my externship for school. My question is can I sue them for slander or defamation of character? Can this at least be grounds for the dean to expel them from school?