don't let it bother you. someday, you'll graduate, and you'll never see most of those people ever again....it'll be the most liberating moment of your life (lol). seriously, nobody is going to care within a month. i can almost guarantee it. and don't worry about the girl who started it either. she'll get what's coming to her. you may not be able to see it happen, but she'll get what she deserves.
and just imagine how awesome it's going to be when you show up at your reunion years from now with your husband! that'll teach them to believe rumors. don't worry about anything that happens now. in a few years, you'll be far from all the drama of school.
good luck!